I meant to write down my stories many times.
The first time, I think, was back at university, in that year when I mostly worked there. Then again, and then again. Each time the thought seemed valuable enough to remember and obvious enough not to write down.
It always ended the same way. The thought would stay nearby for a while, then leave, and never come back again. Clever thoughts do sometimes visit the head; the trouble is that they stay as long as they themselves please, and there is no persuading them to stay.
More was lost this way, I suspect, than went into both my books.
And then I sat down to write the first one.