This is from The Paris Review Interviews, Volume 1:
Q: I would like to ask about your having said that you were very timid about beginning to write stories.
Borges: Yes, I was very timid because when I was young I thought of myself as a poet. Then I had an accident. You can feel the scar. If you touch my head here, you will see. Feel all those mountains, bumps? Then I spent a fortnight in a hospital. I had nightmares and sleeplessness – insomnia. After that they told me that I had been in danger, well, of dying, that it was really a wonderful thing that the operation had been successful. I began to fear for my mental integrity – I said, Maybe I can’t write anymore. Then my life would have been practically over because literature is very important to me. Not because I think my own stuff particularly good, but because I know that I can’t get along without writing. If I don’t write, I feel, well, a kind of remorse, no? Then I thought I would try my hand at writing an article or poem. But I thought, I have written hundreds of articles and poems. If I can’t do it, then I’ll know at once that I am done fore, that everything is over with me. So I thought I’d try my hand at something I hadn’t done; if I couldn’t do it, there would be nothing strange about it because why should I write short stories? It would prepare me for the final overwhelming blow: knowing that I was at the end of my tether. I wrote a story called, let me see, I think, “Hombre de la esquina rosada,” and everyone enjoyed it very much. It was a great relief to me. If it hadn’t been for that particular knock on the head, perhaps I would have never written short stories.