Hahaha! I’m still thinking about places I could improve on a book I published almost eleven years ago.
Welcome to the lovely world of being an author. For me, there comes a point where I’m sick to death of rewriting and self-editing. I put it aside for a couple of weeks, until I can stand to read through it again. When I finish that run-through, if there’s nothing major, I submit it.
But it’s never completely finished, at least in your own eyes. There’s always a tweak that could have been made here, a change there. Resist the impulse and write something new.