The New Yorker has a nice essay by Louise Glück which contains this nearly perfect description of revision in poetry:
I agree the term ‘revision’ does seem a little calm. Isn’t much of life also revision?
Louise Glück on Revision
Marc Di Martino
Poetry
Marc Di Martino 
I loved this article too. And “revision” is far too tame a word for murdering your darlings.
Oh, dear, murder is such a harsh word Sarah!
Not when I start with a GORGEOUS line, the whole poem falls from that line with the rustle of taffeta, and in rewrite THAT’S the line that has to go. Sometimes both the line and I whimper.
Great image, Sarah! The rustle of taffeta…