1. At first your book is still your perfect baby, but you suspect that there is something that could make it better, perhaps some spelling to correct, so you dive in.
2. Two usually hits about the same time you get some "constructive" feed back. No matter how constructive feed back is, anything but, "OH MY GOSH! THIS BOOK IS PERFECT! HOW IS IT NOT A BESTSELLER WITH A MOVIE DEAL RIGHT NOW?" pains me. Some authors are notoriously bad about accepting criticism but still manage to produce masterpieces. Tolkien sometimes responded to mild suggestions by scrapping everything and starting over again. Sometimes it is easy to feel overwhelmed. It is a lot of work, after all.
3. But eventually, you stop dragging your feet and you make changes. You rewrite scenes. You cut and polish and you ask for another opinion. It is starting to look pretty darn good again!
Which generally starts the whole dang process over again.