Oooh, thanks for this thread, illiterwrite! I, too, worry about the "post partum depression!" I've never done this before, so I'm trying to relish every step of the way as I approach publication (just turned my galley proofs in this weekend, so there's no going back now!) and I'm sorta already biting my nails playing the "what if?" game and hoping I don't land like a tree in a forest.
'Course, as some of the others have mentioned, I'm already poking at my proposal for my next one to keep my mind off it (I'm a nonfiction writer, so my rules on pitching are just slightly different than you fiction folks (and don't get me wrong -- I'm envious of your ability to write fiction, just glad I don't have to submit the same way you do! And I just used double-parenthesis, which is sort of a no-no...)) Anyway, that's how I'm hoping to beat back any blues I might have. And also by keeping my expectations managed, too, I suppose....
And look! My book is in my signature! Oooooh....