As much as I would love to join you (and I really would, because I think that NaNo is often good for the perfectionist writer), I should probably stick to editing Insurgent. I know you're going to get boatloads of writing advice, so feel free to discard this as necessary, but here we go:
Don't look behind you. NaNoWriMo is a sprint-- a SPRINT, I tell you. It is full throttle, as many words as you can muster, every single day. You don't get to stop for water-- you have to throw water into your mouth as you run, and if you end up splashing yourself in the ear, SO BE IT.
So I think the sprint-race advice of, don't look back to see how close your opponent is, it will slow you down and you might lose, is applicable here.
Except this time, your opponent is not another person, it's your own draft, chasing you with its sloppiness.
I am familiar with doubling back to address the draft, fixing inconsistencies as I go, tweaking sentences, and so on. I wrote my first manuscript like that, and let me tell you something, and I swear it's true: that manuscript took me a year to finish, and it required more editing than Divergent, which I wrote in less than half that time, taking the "don't look back" approach.
My plan with Divergent was this: just. Keep. Going. I would think of things I wanted to fix later and make a note of them on the document and then just plow on through. Then when I was done, I went back to address the comments, but I never even looked at them until I had written the last word.
So, a few ideas:
1. Keep in mind that when you finish, your draft will be rough, as rough as any other rough draft, and you can't stop that from happening no matter how hard you wish it.
2. COMMIT. That means not even doubling back to check something. I mean it. If you forget a character's name, who cares? Make up a new one and fix it later. (In fact, that's REALLY easy to fix. Find/replace, anyone?) If you double back, even if it's just for a few minutes, you will mess up your momentum. (Probably.)
3. Write everything, everything that comes to mind, even if it's just pieces of different scenes. You can finish them later. You can even write, in brackets, [in this scene, Main Character has a food fight in the cafeteria with Childhood Foe, involving some applesauce in the eye] if you don't feel like actually writing out that scene. Then keep going as if you had written it. It helps.
4. Don't get stuck. Don't even allow yourself to believe you could get stuck. Just start generating ideas and jotting them down like some kind of crazy idea generating machine. Your brain will get used to spitting out five different plans at once, and you really won't get stuck. You may hate yourself when you revise, but whatever, that will happen anyway. The best feeling ever is when you realize that you are racing through a huge stack of scenes and you're still coming up with new ones.
5. Make notes to avoid the "ick, ick, I messed it up, it's messy!" feeling. I find that when I make a note to fix something later, I feel relieved, like I've packed a wound and stopped the bleeding, even though I still need to go back and get it stitched later. (Sorry, that's gross. You get it.)
Good luck, friends.