Sometimes editing can be like having a nest of ferrets living inside your brain. Each ferret is designed to pay attention to one certain shiny thing.
So you'll have an exchange that looks like this while you're trying to be a good writer and Edit Your Book:
Plot-Hole Ferret: That would never work! How the heck does she get from here to there?
Me: True, I don't know why I wrote that. Maybe the Writing Badly Gremlins snuck in and added to the book while I wasn't paying attention--
Typo Ferret: Look! LOOK! You typed "woman" when you meant "women" again! LOOK!
Me: Right, I'll just mark that out with my red sharpie--
Food Ferret: I'm hungry, I wonder what's in the fridge?
Me: Damnit, nothing's changed in the refridgerator since the last five minutes when I stared at it's contents hoping food would magically appear. Now lets--
Distraction Ferret: We need to surf the Internet for...ummm...research.
And then all the ferrets start talking to you at once. At the very least, this looks like I have I have multiple personality disorder. At the worst...well, let's not go there. With drafting, you have one job. One.
Write the book.
Keep writing until you're finished.
There. Easy as a pie. But with revision? You have a ton of stuff to look at. Most writers stay sane by streamlining the process, which is what I have done, but it's still hard not to drive yourself insane thinking about all the details. The typos, and how you've brutalized grammar, and the characters are flat, and the plot doesn't hold up worth a darn, and so on. It's daunting and scary and sometimes you feel like you should just give up and write another book.
But writing is rewriting. You've heard that a billion times, but it's true. If you can't revise your work, you won't be able to tell a coherent story. Revision is every bit as important as drafting is. The cool thing about revision is you get a constant do over.
So just break it down into tiny chunks and ignore all the stupid ferrets chittering away in your brain, least we find you on the street muttering, "Can't sleep, typos will eat me."