Dr Robert Leahy whistles doubtfully when I tell him about the 5:2 experiment. "Is it possible to stop, or drastically cut down, the amount I worry two days a week, while carrying on as normal the other five?" I ask.

"Good luck with that," he says.

Still, Leahy says, he'll try to help. He's a New York-based cognitive behavioural therapist specialising in anxiety disorders. This is my first ever CBT session, although lots of people I know have had it. I like the idea of it. There's no Freudian sleuthing around the unconscious. I don't want me or anyone else sleuthing around down there. God knows what's lurking. Either something terrible, or nothing at all. Either way, what's the point of dwelling? CBT people are likably pragmatic. Your thought process has become skewed; their job is to teach you how to skew it back again.

Leahy asks if I worry every day, if I can't sleep, can't digest my food and can't keep my mind on things. "That's when recurrent worry becomes a problem. Is that what you have? Recurrent worry?"

I nod.

"Does it keep you from enjoying life?" he asks.

"I'd say," I reply.

"You over-think things?" he says.

"Yes!" I say. "I over-think. I get trapped inside an intrusive thought. And then I become convinced everything is about to collapse."

"What do you worry about?"

"OK," I clear my throat. "It used to be that if I couldn't get my wife on the phone, I'd be sure she was dead. She'd be lying with a broken neck at the bottom of the stairs just as my son was reaching up to grab the flex of a newly-boiled kettle. But I don't worry so much about that any more. Now I wouldn't care if something bad happened to them! I'm kidding! I'd care a lot! But seriously, these days I mainly get extremely anxious that I may have screwed up my work and everything is about to collapse."

I carry on like this for a while. But then Leahy cuts me off. "It doesn't make any difference what the content of the worry is," he says.

I feel a flinch of annoyance. If he was a Freudian, I think, I could talk about myself more.

Forty minutes later, he sends me out into the world armed with CBT techniques for retuning my anxious brain.

I begin to understand why the 5:2 method may not work for anxiety. It isn't like meals. It doesn't just dutifully turn up three times a day. In fact, for the next nine days I don't feel even slightly anxious about anything. I'm just walking around fine. I don't credit the method for this, even though I am assiduously doing it. It's just the way anxiety is. Still, I do the Boredom Technique. Twenty minutes a day, on Mondays and Tuesdays, I "flood the worries". I repeat, in "a slow, zombie voice", as Leahy had told me, "It is possible my wife and son are dead" and so on.

Then, on the 10th day, the anxiety descends fiercely. My son has vanished into a dangerous part of Jersey City, New Jersey, without his phone. We haven't heard from him for three hours. I'm sitting on a plane. It's at the gate, waiting to leave. The very last thing I do before I have to turn off my phone is Google "Jersey City shootings". There are a lot.

For those of you without an anxiety disorder, what it feels like is someone inside your face, vigorously sandpapering your nerves. The sandpapering can go on for hours. When it subsides, you're left feeling raw and tired. The feeling is so overpowering, the last thing on my mind is the stupid experiment. But I give it a go. "Is this a productive or an unproductive worry?" I think.

Leahy had told me to make a distinction between productive and unproductive worries. Is there any productive action I can take that would possibly solve this problem? If no, it is an unproductive worry.

This is an unproductive worry. I am on a plane, helpless to prevent the person pointing a gun at my son from pulling the trigger. So I move on to the Boredom Technique.

"It is possible that my son is dead in Jersey City," I mutter. "I want my son to be dead in Jersey City."

When I first heard that this was a CBT technique, I actually gasped. But it makes sense. There is no connection between a thought and reality. To my surprise, the Boredom Technique starts to work. I can feel the anxiety begin to ease slightly. Which is why I have no justification for what I do next. I think, "I'm on a plane. These are special circumstances." So I reach into my bag and take half a valium.

This works straight away. I'm fine for the rest of the flight. Then, on landing at JFK, I discover that he is dead. I'm kidding. He's not dead. He's home. He was just at a friend's house. I said he was dead because CBT specialists advocate facing the fear by writing it down. I feel groggy from the valium. I never take valium. That one had been sitting in my bag for weeks. I decide to make more of an effort with the 5:2 technique.

So I do, for a fortnight. I regularly do the Boredom Technique. I try also to "rock and roll and commit to the action", even though I don't love the choice of phrase.

"When you windsurf," Leahy had explained, "the key is to rock and roll and commit to the action. Just fucking go for it. Don't hesitate. You will or you won't fall into the water. The only meaningful way you can live your life is to be alive."

I can't say if there's a connection, but my anxieties are pretty nonexistent throughout the period. Who knows why? But one thing is certain. A story Leahy told me sticks in my brain and really does help. It's the story of a study conducted by Tom Borkovec, a psychology professor at Penn State University. He interviewed a bunch of anxiety sufferers. One of the questions he asked was how they handled it when something bad really did happen to them. "Seventy-nine per cent said they coped with it better than they thought they would," Leahy said. "Worriers may not be good at coping with imaginary problems, but they're actually good at coping with real problems."

This is something I've always suspected to be true. It's a comforting thought. I think it will continue to help, more than two days a week.

How to make it work

• Make a distinction between productive and unproductive worry. Ask yourself, "Is there any productive action I can take today that would possibly solve this problem?" If not, it is an unproductive worry.

• The Boredom Technique. Take the unproductive worry and repeat it to yourself, slowly, like a zombie, for 15 minutes. Juggle the words around so they make a nonsense sentence, unlinked from meaning.

• Face your fears. Say, "I hope my wife dies in a car accident." "I want to screw up my work."

• "Rock And Roll And Commit To The Action." Live fully in the present moment. Forget "What if?" worries. The only meaningful way you can live your life is to be alive.

• Anxiety Free, by Robert Leahy, is published by Hay House at £9.99. To order a copy for £7.99, including UK mainland p&p, go to theguardian.com/bookshop.