I was just about to go to sleep. There I was, last cigarette of the day crushed in the ashtray and glasses set aside on the coffee table, getting SO comfortable- and then BOOM! Idea.
I had been looking for the way into this short story idea I've been kicking around for a couple of days, without success. And then, right when I was shutting down for the day, there it was.
And this is one of the simplest ideas in the world really- when that happens, you can do one of two things. One, you can get back up and work that idea, get it started, get something down. Two, you can let it go and just go to sleep. Maybe the idea will still be there when you wake up- maybe. Or maybe it will be gone, off to that landfill of ideas that almost happened.
My suggestion would be that you get up.