I live by myself in a good place, the best sort of place a woman like me could imagine. In fact, it’s all I did imagine for years on end. I rent rather than own it, but that’s no hardship. I’ve never felt any particular angst to own property, which is just as well since I live in London, a place where I could no sooner get a mortgage than a giraffe. Owning a home has always felt more like a burden, like an end to things, to me, than it has felt like comfort. I did always dream, though, of renting somewhere beautiful and living alone there – and now I do.

On the days I spend here without anyone else, I wake up at 8.30 and feed my cat. I watch her eat her disgusting, stinky food with satisfaction, glad I’m able to keep another creature beyond myself alive. I make coffee and wander about the flat a bit, wiping surfaces, washing tomato-laden pots. I go for a walk or to the gym, and then I work. I write. I send emails. I complain or speculate about everything I’m doing constantly to my friends. For lunch I blitz the vegetables in the fridge into a soup, or else walk down the road to the pub for a sandwich, and come back and work some more. I gaze adoringly at the cat. It becomes evening and I might drink a glass of wine, sometimes a bottle. I cook dinner and eat it in 13 minutes while watching MasterChef. I read for an hour. I work a bit more. Sometimes I watch a film. This is the life I have designed for myself, the life I never thought I would be so lucky as to have. Then it is time to sleep.

In my comfortable bed I read more and turn out the light and within 15 minutes I hear a jolt, a metallic clank outside in the garden. I reassure myself it’s just an animal. I try to sleep again. I drift off. Then there is the apparently unmistakable noise of the back door being jostled. I fly upward in my bed like the girl in The Exorcist, thrust into the air what feels like 2ft from pure fright, and once there and awake I keep completely still. Now, finally, it is happening. The comeuppance for my too-blessed life, for my choice to live alone. Something terrible is taking place. Another soft click from the direction of the front door. Now my entire body is flooded with adrenaline and my mouth arid.

I try to recall through my panic the things I have done to mitigate the chances of an attack: the locks all double bolted, the keys taken out and placed far away so that if a person smashed through the glass they couldn’t easily open them. When I was terribly afraid one night I took a small sharp knife and hid it in a secret place accessible from where I sit in my bed. I can take it out without making much noise. There is another creak from the hallway, and I silently retrieve the blade from its hiding place and hold it in one hand and my phone in the other. I sit there like this, rigid with conviction and terror, for more than an hour. No thoughts pass through my head in this time apart from keen listening for the next noise and what direction it comes from, strategising my escape. Can I be sure they are coming from the area I think they are, or could they be coming from both sides? Is it wise to lock myself in a toilet? Am I strong and small enough to break through that window if necessary?

Eventually, I accept that I am too frightened to move to check whether someone is outside my bedroom door one way or the other, and that the elapsed time means that it is unlikely they are there. I put the knife back in its place and turn on the two lamps on either side of my bed, and a podcast so that it might sound to somebody outside that there are several people in this room. I lie back down and practise some breathing exercises to try to sleep. It’s now perhaps 4am and I have lost half of my allotted rest. I am useless and angry when I wake up, aware of the absurdity of my fear and that I have allowed it, by indulging, to ruin my day.

This happens two, three, sometimes four times a month. Twice as many times as that I am woken in the middle of the night with dreams that somebody is entering my window or sitting on my bed, terrors which are both more and less intense because they are unconscious, but which mean just the same that my sleep is robbed and fragmented, my body feeling as if it has been through a battle when it wakes in the morning.

I have always been what could kindly be described as “nervy”. I panic inordinately, reacting with huge exaggeration to ordinary aural surprises. Sirens, shouts, my boyfriend gasping, “Oh my God!” when he looks at his phone (Spurs were down one nil). Ghost trains, even the most comically amateur, were not something I could tolerate as a child. When I hear a fox rustling in the garden or see a flash outside in the dark – the light of my own bathroom – the momentary fright I get is so ludicrously powerful, and so physically so, that the rest of the night spirals. But why? Why am I like this, so susceptible and easily overwhelmed? Do I truly believe it’s likely that a prowling man is going to break in through my window to hurt me?

I read voraciously about Ted Bundy as an adolescent, the first of the iconic American monsters to catch my attention. I picked up Ann Rule’s pulpy book, The Stranger Beside Me, at a school jumble sale and pored over it with appalled titillation. Sometimes he approached his victims in daylight and in public places, car parks and beaches, but his first few were women asleep in their beds – women in basement apartments like mine. I spent the subsequent 15 years consuming true crime with unattractive compulsion. There was Unbelievable in 2019, the Netflix show based on the true story of a serial rapist who broke into apartments and attacked his victims as they slept. He lectured one woman smugly about the inadequate safety measures which had left her open to his predation. The show sparked conversation among women about their terror of solitude, the exhausting knowledge of their own perpetual vulnerability.

All my life I have loved to walk alone at night. As a teenager making my first clumsy forays into pubs and partying, the walk home with my Discman was often the part I prized most. The processing and the narrativising were better than the experiences themselves. I take an admittedly thick and wrongheaded pride in the fact I feel no fear about doing this, that I don’t let tragic stories – about women attacked in circumstances like those I willingly embrace – change my behaviour. I like to think I have mostly refused to let the potential evil of the world hamper my freedom.

This makes the sporadic paralysing fear which overcomes me in the safety of my own bed all the more humiliating and ridiculous. Message boards and articles describe women who keep muddy men’s boots outside their doors to intimidate intruders, who sleep with hammers under their pillows, who tell nobody that they live alone and put male names on their delivery orders. They have intricate set-ups involving bells strung up to alert them if the window is jarred. I thought I was a different sort of person to this, one able to operate within reason, according to the actual likelihood of harm rather than intangible bogeyman, but it turns out I am not.

Does my submersion in true crime shows and books, in the extraordinary and rare stories of famous sadistic crimes, mean I believe they are more likely to happen to me than they are? Or is it that the knowledge of such things ever happening warps us; that they could take place even once in the history of humankind, that it is possible for a person to enjoy another’s pain to this degree? Maybe that knowledge stretches the mind to encompass more oblique danger than it can accommodate; more than logic can successfully deny.

Beyond the literal, material sadistic intruders I fear when I am in my spirals, there is something bigger and more difficult to define. They suggest a mass of malevolence and ill fortune of which they constitute only one small part. In my waking life I do not believe that someone is going to break into my home as I sleep and commit acts of violence against me. In the moment, something else is taking place. It’s the feeling of all future disaster encroaching in the indifferent calm of the dark, my thoughts unfettered in the pre-dawn hours turning invariably to death.

In our irony-exhausted culture it feels almost laughable to say it plainly, but I’ll say it all the same: night is when I really burrow down into the knowledge that everyone I know is going to die. Sometimes I consider them one by one, every person I love and the different ways they might go, which circumstance I could learn to bear, which ones would drive me mad. It’s a lonely and ultimately inconsolable despair to find oneself wading through in the wee hours. Perhaps it’s easier to focus on an errant creak, the possibility of intrusion. Perhaps, too, this is why the feeling of my boyfriend in bed beside me is such an efficient remedy. Not because he can fight off monsters any better than I can, no offence to his prowess, but because it is easier to disbelieve the truth of death when I can hold on to some other creature who is living and beautiful and strong, someone so bright and apparently infinite that it would surely be impossible for them to ever die.

I have become worse rather than better since beginning this relationship. When I was always alone I rarely reached such high pitches of fear. I rarely noted my solitude at all; there was no other way to live. Now that there is one, now that nights alone are mostly optional, I struggle. I say goodbye to him on a Sunday evening, dread filling my chest, and I know that if I asked, then he would stay or I would go with him, and I have to forge agreements with myself not to do so. I battle as I always have done between the force of my need for others and the force of my disgust towards dependence. I suspect I will have to grapple with those competing interests for the rest of my life. I can’t accept that I need another person to do something as basic and necessary as sleep. It would be too dangerous to concede such total reliance.

Instead, I push through on the nights I am alone and afraid. When sleep evades me totally I wait until dawn comes, slip on my headphones and walk out into the streets. There, no matter how early it is, I see that life exists, cyclists and bedraggled revellers and the train station coffee shop setting up. I listen to music or to a podcast about something amazing, something that happened in a place I’ve never been to but could travel to one day if I really wanted to.

I am glad that wandering outside is where I feel safest and happiest, because here I’m reminded of how much I love the world and the people in it and everything I don’t know about them, and that whatever fear I feel on my own is only a kind of proof of how strong that feeling is. On these mornings I am filled with the sure knowledge of the ongoingness of things and how miraculous that really is, and that knowledge is just as real, or even more so, as the knowledge of endings which comes in the dark.

Acts of Desperation, by Megan Nolan, is published by Vintage at £8.99. Buy a copy for £8.09 at guardianbookshop.com