"Huzzah! I have written the book I was supposed to write! I will set it aside for a couple of months to let it stew so I can put my finger on what, precisely, is off about it. Doubtless it will be an easy fix! No biggie!"
Two months later:
"I figured out what was off about it! It was the entire plot of one of the dual POV's! I will change that but keep the other one, and it will be a less-than-easy fix, but no biggie!"
One month later, aka last night, aka three weeks before deadline:
"Oh, just kidding! Actually turns out I wrote ENTIRELY the wrong book, start-to-finish, and need to just go ahead and write A WHOLE NEW BOOK. No biggie! NO BIGGIE! HA HA HA WHATEVER NO BIGGIE AT ALL NO BIGGIE NO BIGGIE NO BIGGIE."
If the highest praise you can give a book is that nothing is wrong with it, everything is wrong with it. I refuse to turn in a mediocre book when I know I can do better.
I just wish the whole doing better thing came, you know, THREE MONTHS AGO.