In an interview with the Wall Street Journal, novelist Scott Spencer ("Man in the Woods") talked about how he goes about rewriting his first drafts:
"I find starting from the beginning in a new draft better because you can stray further from the confines of the original draft. There's something inherently conservative about working your changes into the draft you've already completed. Also when I'm doing that close kind of editing and working within a structure, I'm less subject to flashes of inspiration. But the previous draft is right there, in a pile next to my keyboard, and I'm reading it while I'm working on the next draft. There's something about the movement of my fingers over the keyboard that connects me to the part of my brain that writes."
Sounds like a lot of work, doesn't it? That's consistent with what he says about the ratio of inspiration to discipline in writing a novel:
"One to three. The three is discipline."
My answer would be more like ten to one. And yes, the ten is discipline.
(It's easier to write when you have proven practices to follow. You'll find them in "Your Writing Coach," published by Nicholas Brealey and available from Amazon and other online and offline retailers.)