That's why it's good to edit for a while, and then take a month or more away from the book to let your brain cool down and get refocused on the story again. Sometimes what I'll do is write on one book for a while, then move on to the next, and then another before coming back to it. That's what's so nice about having a "todo" list as long as mine is. You always have lots of variety in your writing to keep you from hitting that point of over indulgence in one particular book.
