How did it happen?

I had an idea for a story on the train home yesterday. more than an idea - a voice, and it was strong enough for me to scribble a page or so when I got into bed. I was too tired to write the whole thing in a wonderful inspired gush! someone once said that was the only way to write a story - I think I haven't written one since. So, how did it happen?

1. I heard Ann Enright read a story at the Small Wonder Festival at the weekend. I also heard William Trevor and a story by Richard Yates (read by Lionel Shriver but still a man's story and a man's voice). This gave me a voice (an outraged wife), a structure (she forgives him), a start (the death of the girl he's been having an affair with).

2. This is not what I'm going to write about, but it is about a couple, relationship breakdown, my own breakdown and how my husband dealt with it. I haven't written about this yet but I have been thinking about it a lot. Maybe it's time now.

3. I sent off a chunk of my novel to my supervisor on Monday. Maybe this symbolic expulsion has freed up the next writing project.

Or is it some mysterious combination of all three?