There's always a period of noodling with it after the major rewrites ... I don't seem to be doing much but it seems to be getting much better. I've never figured out if my little changes are really improving things that much or if I'm just getting used to it. I worry that my judgement of the process is not reliable and it's either my ego telling me it's better or maybe I'm just getting the form so set in my head that I start seeing it as "the way it's supposed to be." I can still be critical at that point but I never like to think I'm fooling myself. Of course sometimes little changes matter a lot.
Many writers I know have a person they trust to read it and to bounce stuff off of. I used to have someone like that but don't any longer. I have to say ... it can be VERY helpful!
I have a critique partner and it's been incredibly helpful. As a reader and a writer, she catches things that I wouldn't even think about because I'm too close to the story.