I think I started writing plays as a way of expressing the things that I couldn’t say. I’m a constant idiot in conversation – I always seem to sound either smug or stupid. Writing plays was a way of winning the conversation by controlling the conversation. I became “super talk” – the king of all arguments – impressing everyone with my wit and vivacity. Sadly, none of those plays were any good. I then went through a stage of utter self-hatred and destruction – where everything I wrote was about how disgusting I was as a human being, and how much I hated the world and particularly me within the world. Those plays were still largely shit, but were slightly better. And then I think – I hope – I learnt how to write about other people – and then I think – I hope – I learnt how to write about myself again with a better sense of balance.

I wrote about 22 plays before When You Cure Me, which was staged in 2005. I occasionally get them out and have a read – thinking maybe there’s a thought or an idea or even a turn of phrase that I could use for something new. There’s not. They’re dire. Even now I’m not quite sure why I persevered. Everyone told me to do something else – the criticism was wide-ranging, but mostly very critical. My endurance was partly due to love and partly due to utter dependence. I wrote my first play because I wanted to direct something at university and couldn’t afford the £65-a-night amateur fees. And from the moment I started writing, it was instant, I grew slightly obsessive about it. I was a terrible writer, but utterly obsessive. Before I got married I was a 16-hour-a-day, seven-days-a-week man. Now I’m 10-hours-a-day and my wife and I have a contract which states that I take at least half a day off a week. All of which is to say, I am entirely psychologically dependent on writing, it gives me stability when all else is failing. And I spend way too much time doing it.

I was taught, as many others were, by Simon Stephens as part of the Royal Court young writers’ programme. He taught us all a huge amount, but there was one thing he said in particular which I’ve puzzled over ever since – that every writer has a myth. A story that they return to again and again – something which drives them – something which gives their plays a sense of themselves. That it’s not a writer’s job to identify his or her myth but that it’s there – in the background – if you look for it. Simon, when I asked him, said, after quite a lot of thinking, he thought his own myth was probably “listen to children” – though he said he wasn’t sure and other people might be better judges, and when I’ve mentioned it to him since he had no recollection of thinking that. But watching his work through the prism of “listen to children” I’ve found quite a beautiful experience. I don’t know what my myth is, and I’d struggle to nail it down, but I think it has something to do with help – what help is, and the struggle we all go through trying to help others, and perhaps what failure to help looks and feels like. Like I say, I could be wrong. And it feels self-important even guessing at it. But there is something about thinking that there’s something I’m trying to say – that I have a myth – that’s always felt somehow useful to me. Both in looking at others and worrying about myself.

The first time I thought I might have a future as a writer was as a result of a phone call from an amazing woman called Teresa Topolski (who my play Bunny is dedicated to). I’d been sending off letters to theatres for a while, and unsurprisingly not getting very encouraging letters back. In fact, I once got the opportunity to look through the Bush Theatre’s “reader pile” and discovered the notes written on my first play I sent them which concluded with: “This play is, on the whole, irritating.” But Tessa thankfully saw something even in these terrible irritating plays – and called me up – this is the days before mobile phones – on my mum and dad’s phone – and said she thought my plays were interesting (I’d sent the same three to her at the Tricycle) – I remember playing the message to my little sister approximately 24 times. Every play I subsequently wrote I sent to her, for about three years, and she constantly stayed interested and un-irritated by me. She built my confidence, she encouraged me to look at my writing in a new way. She gave me the courage to approach agents and theatres again and I managed to secure an agent who also saw something passably interesting in me – Rachel Taylor – who also proved brilliant at reading and who remains to this day the most ferocious of readers of my first drafts.

Christine Entwisle and Jo Eastwood in Jack Thorne’s latest play, Hope, now at the Royal Court, London. Photograph: Tristram Kenton/Guardian

And at the same time – through the Royal Court young writers’ programme – I fell in with another writer – Laura Wade – who became a close friend. And we set up a system where I read everything Laura wrote (and everything she wrote was, of course, brilliant) and she read everything I wrote. These three worked me hard. They were perfect readers – tearing apart that which was important to tear apart. And eventually I sent out something – then called A Bedroom – which they thought might actually work onstage. Tessa thought me better suited to the Bush than the Tricycle. She took it to them. And the Bush commissioned me to rewrite it, which I did under a new title, When You Cure Me.

When You Cure Me was written partly as a result of this illness I was struggling with. I had (actually still have) a condition called cholinergic urticaria. Which is a strange version of a sort of chronic prickly heat. I’m allergic to heat in all its forms – natural, artificial and body – any stimulation left me covered in painful red welts. At my worst I was lying flat in my parents’ house with all the windows open – in December – in Wales – and every time I moved I was getting an allergic reaction – I was allergic to moving. It’s an unknowable condition that various doctors tried me on various medications for, and it came on very suddenly when I was 21 and caused me to drop out of my final year of university. Which was annoying and frustrating and made me feel like a failure. Now it’s under control, then it was brutal. And no one really knew how to help me with it. Friends who kindly wrote me postcards would get nine-page letters in reply, they’d write back again a week later and immediately get another nine pages, eventually I scared them all away through sheer exhaustion. My mum made me a cake a week but found my bedroom really upsetting. I was told by one doctor it was possible I might not get better, and by another that it was all in my head. I felt very very sorry for myself and angry with the world. So in the play Rachel is me, but so is Peter. And hopefully neither is me too. I think it’s a play less about someone getting better, and more about someone learning how to recover, and how to help the people around her recover too.

That play was directed by Mike Bradwell, who said there were three answers to every question I can be asked as a playwright: “yes”, “no” and “moo”. Moo was the get-out clause, the answer to the unanswerable question, or the question best left for the process rather than for the playwright’s head. It’s a system I still try to use to this day. I struggle quite a lot in rehearsals, partly because I’m shy, partly because I still don’t really understand the work that actors and directors do. I love the magic at the end, but the getting there – the wrong turns that are necessary to make something work – I find slightly beguiling and worrying. So When You Cure Me remains the only play I attended every day of rehearsals for. I remember watching the dress rehearsal from the back of the room, which was too hot for me to deal with. But that press night – I’ve never had a feeling like it – the actors did something extraordinary and I was floored by the whole thing.

• This is an edited extract from the introduction to Jack Thorne Plays: One published by Nick Hern Books. Jack Thorne’s new play, Hope, is at the Royal Court theatre, London, until 10 January; script published by Nick Hern Books. Buy the books at a special price including freek UK p&p at bookshop.theguardian.com or call 0330 333 6846

• Mark Lawson meets Jack Thorne