Several of my friends are doing NaNo. Also, I was lucky enough to teach a class called Prepping For NaNo and some of my students are reporting back to me.
Actually, the ones reporting back are the ones who are having a great time writing because of all the prep work we did last month. Which makes me smile.
We can't go into all the things I taught last month. But there are two tricks you really should try if you hit a brick wall.
First, write a one-paragraph ditty stating what your book is REALLY about. Don't say details. Just give yourself a straight-as-as-arrow rundown so you can see your story.
i.e. The hero and heroine must catch a killer, but she's already been arrested for the crime and he's the DA prosecuting her.
Driving back from Vegas, where the heroine ran when she realized she couldn't marry her fiance, the hero and heroine are incredibly attracted. But she's the boss's daughter and he's a total stranger to her, and when push comes to shove, the hero also realizes he can't get involved with another woman who's already committed to a man. Because no matter how much she seems to like him now, when they get home, she could see her distraught fiance, decide she really does want to marry him after all, and the hero will be the one with the broken heart.
Reading either of those could get and keep you on track when you're at a loss for what to write. You all probably like the second one better because it drops in a few plots points. But when you're in a tizzy after having written 33,000 words and your brain is sort of mush, either one would remind you of the heart of your story and help you to refocus.
Another reason we get off track is that we get too picky. You've written 17,500 words that you believe are golden, but the next day everything you want to write seems trite.
So you stall.
The answer to your problem is to let your brain go. Since you don't want to spoil the WIP with its golden 17,500 words, don't write a scene...do a could, might, must and should list.
This could happen.
This might happen.
This must happen (to make the plot work).
This SHOULD happen...ie. in a romance the hero and heroine SHOULD kiss and maybe even make love a time or two. The conventions of your genre need to get into your book too.
Anyway, make this "list of scenes" for the remainder of your book. The scenes that could happen, the scenes that must happen, the scenes that might happen (but you're still vetting them), the scenes that should happen (get those genre conventions in).
Let your brain go wild. Come up with ridiculous answers. Come up with trite stuff. Come up with anything you feel like. Why? Because you're not going to use all the scenes in this list. It's really only a list of suggestions for you to look at and ponder to wake up your brain.
So go nuts. Give your brain lots of potential scenes to look at every morning. Some days you really will pick 2 or 3 of them to write. But other days that list of scenes will serve merely as a way to wake up your brain. You'll say, "Yeah, that could happen ... but wouldn't it be better if..." And guess what? You're writing.
And isn't that the point? ou're looking for ways to get yourself into the story again...and if that one-line/one-paragraph ditty about your story doesn't work, then the could, might, must and should list certainly will.