As a well-adjusted middle-aged man, I like to define myself by the things I don’t have. I don’t have a scarlet Lamborghini or a conspicuous tattoo or a 22-year-old girlfriend to jumpstart my libido. Nor do I possess a penchant for extreme sports or expensive psychotherapy. Midway through my fifth decade, I’ve avoided the obvious pitfalls and reckon I’m coping quite well, which is why I am on my way to discuss the male midlife crisis with the therapist Andrew G Marshall, who has written a book on the subject. It’s a task that requires a cool and dispassionate eye. We will be like two doctors, I decide, objectively diagnosing the problems of others.

Inside his therapy room, Marshall directs me to an armchair and stoops to pour out some water. First impressions could hardly be more reassuring: Marshall is a soothing, sober man in colourful clothes. He asks about my background and my health, moving from my childhood to my present circumstances. I respond as honestly as I can, still confident I’ll be given the all-clear. I tell him I sailed past my 40th birthday with no problem at all. After that, admittedly, there was a difficult spell, one that lasted perhaps four years. I list all the things that happened. I tell him that my relationship broke down and I moved out of my home. I tell him my best friend died suddenly, which threw me for a loop. I mention that my father fell ill. Oh, and that I also got married. I tell him that I then had a second child to set alongside my 11-year-old daughter from the previous relationship. I tell him I quit my job and quit London, and that we now live out west. I tell him I think that’s about it, although there might be some stuff I’ve forgotten. But by now I’m out of breath, shaken. Recited as a list, those past four years sound positively existential.

Marshall jots notes in his pad. He asks who I turned to for help during this difficult period. I tell him I didn’t really turn to anybody: I went through the worst parts alone. Why would I want to have people seeing me as a mess?

“It’s quite interesting,” he says. “You belonging to what we nowadays call the metropolitan elite. Most of my clients, by your age, have had at least three therapists. Whereas you went through this incredible period and not only did you not seek professional help, you actually detached yourself from your friends.”

I nod dutifully, and yet something he said has already stuck in my craw. I don’t consider myself part of the metropolitan elite, and I’m annoyed that he would blithely stick me in that box. Nor, for that matter, am I convinced I’ve had a midlife crisis, despite the bald evidence of those torrid four years. But that’s the nature of cliche. We may see ourself as one thing, unique and specific; the world sees us as another – as a social demographic or a cluster of symptoms.

Marshall’s own interest is based on both personal and professional experience. His partner died when he was in his late 30s and this pitched him into what he describes as “the bleakest period of my life”. Meanwhile, all around, his patients were navigating a similar set of hurdles. The Office for National Statistics reports that 40- to 59-year-olds are the most anxious age group. Marshall believes this anxiety is sparked by a sudden awareness of mortality and a fear of failure; the nagging, nightmarish sense that we will never fulfil our true potential.

No one wants to own up to a midlife crisis: the condition is redolent of too many bad jokes. On setting out to write his new book, Marshall even deliberated before putting the term in the title, concerned that the mere mention might scare readers away. Finally, he opted for a cunning disguise, referencing the condition while denying its existence. The book is called It’s Not A Midlife Crisis, It’s An Opportunity, subhead: “How To Be Forty- Or Fifty-Something Without Going Off The Rails”.

Marshall has seen many casualties in his time – people who, when faced with the challenges of middle age, promptly crash and burn. “A lot of people flunk the test,” he says. “They anaesthetise themselves – with drink, generally. Or with computer games, or pornography. Or with work. And if you don’t answer the questions, you become bitter, closed off and cynical.”

I start to wonder whether I flunked the test. Marshall certainly seems to think I was guilty of closing myself off. He says, “I’m getting a very strong message that you’re not allowed to be vulnerable. That you need to be loved, yet, when things get difficult, you withdraw from everybody. It’s a strange dichotomy. Because on the one hand you’re an open book in a rather controlled way, in that you’re a journalist and therefore in charge of the words. But the rest of you is completely closed.”

“I don’t think I was completely closed,” I say. “I just didn’t want people to see me in disarray.”

“I’m sorry,” he says firmly, “but that’s completely closed. You only wanted people to see the mask.”

“OK,” I say. “Fine.”

And yet, actually, it’s not fine: his whole premise is bullshit. Look at us here. Look at what we are doing. Almost shouting, I say, “It’s a ridiculous thing, you saying I’m closed. I’m going to write this bloody session up for everybody to read.”

Marshall smiles, unperturbed. “Yes, well,” he says. “Often in the second half of our lives, we have to do all of the things we didn’t do in the first.”

***

The term “midlife crisis” was coined in 1965 by the Canadian psychologist Elliott Jaques. Marshall believes the label has now outlived its usefulness. He prefers to call it “the midlife passage”. Approached in the right spirit, he says, this is a chance to engage with the big questions: who am I? What are my values? What gives my life meaning? You can meet your true self. You can become your own person.

Marshall has devised exercises to smooth our progress. He describes a simple counting meditation to reduce anxiety, explains how to “record your feelings”, and the events that trigger them. He also invites us to chart the highs and lows of our lives on a graph, moving from infancy through to middle age. I try this last one myself. The line leaps and dips with abandon. It makes my life look like a series of cardiac arrests.

The way Marshall tells it, there are three obvious routes through the midlife passage. Fail the challenge, and you suffer what he describes as an L-shaped life, where you plummet to Earth and then essentially flatline until death. Pass the test, and you win the U-shaped life: a glorious upswing, a brilliant late bloom. Then there is the third option, the joker in the pack, the switchback ride of the W-shaped life. This occurs when you reach for the quick-fix solution (the thrilling affair, the scarlet Lamborghini), or what Marshall calls “the myth of the great other”. The effect can be instant, galvanic. But it’s an artificial high, a dead cat bounce that leads only to more heartache.

Naturally, this makes me wonder about my own circumstances. The storm has passed; I have a new life in a new city. My days are a whirl of nappy changes and country rambles, augmented with odds and sods of semi-regular work. I’m pretty sure it’s not an L-shaped life. But is it a W or is it a U?

Out of the blue, I find myself telling Marshall about a man named Miroslav Novotny. I think he’s originally from the Czech Republic; he speaks rudimentary English. I picture Miroslav Novotny as something out of an Edward Hopper painting, a study in urban loneliness. He wears his trousers too high on his waist. He uses too much hair tonic, smokes discount cigarettes. I explain that my wife and I devised a game we would play when driving the outskirts of south London, in which we work out where Novotny would most like to live. So we place him in that impersonal block of flats out by the A20, or eating egg and chips inside some sad greasy spoon. Novotny, of course, does not exist – we made him up – yet the uncomfortable truth is that he’s the alternative me. He asks nothing of anyone and gives nothing in return.

All at once, I can see it clearly. “If I had taken a different route out of all this, I’d be Miroslav Novotny,” I say. “And I’m glad I’m not. But there’s a certain comfort in being Miroslav Novotny.”

Marshall nods. He says, “Life is small but it’s safe.” And I nod back in relief, because that’s it exactly.

Did I have a midlife crisis, I ask Marshall.

“Yes, you did.” He adds that it is not always advisable to throw absolutely everything in the air, as I seem to have done. But that’s by the by. Stable door, horse bolted. “You have been through it and navigated it and have had a reasonably soft landing.”

He asks if I have any further questions. So I ask whether he sees the midlife crisis as a peculiarly first-world problem, a kind of luxury accessory afforded to those with too much time on their hands. I’m not sure you have one if you’re under siege in Aleppo.

Marshall has his doubts. “It’s not a case of having too much time on your hands,” he insists. “It comes with a great mallet and hits you over the head. So I think it’s something intrinsic in mankind. The first world-third world distinction is the wrong idea.”

My second question is more personal: I ask if he believes it’s possible to be both horribly anxious and basically happy, because that’s how I’ve been feeling for the past year or so.

“Yes, I think you can,” he answers. “But if we were to continue working together, the anxiety is something we would be looking at. I think that anxiety and anger could be the keynotes for you.”

He is keen to accentuate the positive, though. “It sounds to me like you have completely transformed your life. You’ve gone from closed to open. From work focused to family focused. From self-sufficient to more connected. From the small world of…

“Miroslav Novotny.”

“From the small world of Miroslav Novotny to the larger world of family and children and a new city. But the anxiety is something I would be working on. Anxiety and depression are like brother and sister.”

I walk back to the tube in something of a daze. I feel as though I’ve spent the past 90 minutes being dangled upside down by the ankles, watching all the detritus falling from my pockets. Some of this clutter was harmless ephemera, but other bits were jagged and rusted. Some were foul-smelling, some smeared with dried blood. With them gone, I feel lighter.

***

One month later, I meet Marshall again, this time in a bookshop above a cafe. It’s late August, and the therapist is on holiday. He’s bare-kneed in tan shorts, with a natty straw hat perched on his pink scalp, a copy of Graham Swift’s Waterland parked in the crook of one arm. Seeing him here is slightly disconcerting, like bumping into a teacher away from school.

He asks how I’ve been and I assure him I’m fine. I tell him, in fact, that I’ve been suspiciously fine. I’ve started to wonder whether the session itself was a kind of quick fix. I worry I painted myself in too positive a light; I worry he moved too quickly to endorse my depiction. This would normally be about a six-month process. We went through it in about 90 minutes flat.

“Well, yes,” Marshall agrees. “It’s not the best way of doing it, so you have to be careful. I mean, if I had been aware of some really horrible stuff, I would have skated over it, because I don’t want to open up that can of worms. If we saw there was a total car crash in the wings, I might well have acknowledged it – but I wouldn’t go up and peer through the window.

“But, happily, there wasn’t. And even if there was, I had the sense you’d come through it relatively unscathed.”

I feel I’ve made peace with my crisis, but what comes next? I want to know what other hurdles I’m going to face in my 50s, to steer clear of more trouble, if I can.

But the therapist grins. He’s in holiday mode. “What comes next? Well, wonderful times. If you’ve done the work of the middle passage, then you’re in a very good place, the sunny uplands of life. The next question is not what gives your life meaning, but what gives meaning to everyone’s life. It’s a more spiritual inquiry: the self versus the infinite.” Another grin. “I’m not even sure whether therapy is the right place to answer those questions. You may need to roll up your sleeves and go and do it yourself.”

The house where I now live is perched high on a hill, a steep 15-minute climb from the nearest train station. I try to make this journey on foot as often as I can (if I’m losing my hair, I figure I can at least shed some weight along with it). Sometimes I wonder how I must look to the motorists driving by. A sweaty, middle-aged man with a red face and bad posture, sometimes pushing hard at a buggy for added comedy value. The man is a wreck. Every step’s an ordeal. But near the top of the hill, the road swings out from the shadows. The city drops away and the horizon is endless. And this, I decide, is my favourite part of the journey. One might almost be entering the sunny uplands of life, approaching a house that feels very nearly like home.

• It’s Not A Midlife Crisis, It’s An Opportunity is published by Marshall Method Publishing at £12.99.