The always interesting texts from "Writers Ask," the quarterly magazine produced by Glimmer Train, include a quote from Charles Johnson that could apply to all writers, whether of fiction or non-fiction.
A first draft of a novel or story should be written with the intention of seeing if you have something worth pursuing. You begin to clean up in the second draft. You take out what doesn't fit, and you fill the holes of the first draft. It's not until the third draft that you can settle down and begin to revise. After that, you might go through twelve or twenty drafts to improve and refine. To me, that is not a lot to ask. Nothing is perfect. I'm not going to say certain things don't approach perfection, but the goal is to have something that is as consistent, coherent, and complete as you can make it in that moment. If you revise thoroughly, that moment might be a long moment. It might endure for decades as a work. Writing well is the same thing as thinking well.