I do a version of this every year and well, ahem, we could probably revisit those but NaNo is all about creating new words so here we go.
1. All writing advice is just that - advice. Suggestions are based on what worked for the person giving the advice and that includes everything here. So any advice that works for you is great. And any advice that didn't work for you, stop using. If anyone had a magic key, then literally all of us would be using that and there wouldn't be a need for so much advice. Your job is to figure out what works for you.
2. There will be ebbs and flows. Some of that is normal - life, plot problems all happen. If you hit a slump that's fine. Your job is to figure out what things need to change to get you out of it. Beating yourself up about it is not a useful part of that.
3. Back everything up. Even the parts you think are crap. Print it out, email yourself a copy, take picture of your notebook, do not let there be only one version.
4. Try things you haven't tried before. If you've never been to a write in, try it. If you've never tried writing in a library, try it. If you've never tried writing from your couch while checking in with the NaNo sprints team, try it. Anything that tanks your word count, don't try again. But just like (I hear) people who exercise get bored with the same old same old, your brain does too. So jazz up the routine.
5. Decision fatigue is real. So if you find at the end of the day you can't figure out what your characters need to do next, try deciding earlier, even if you can't write earlier. Take a voice memo, write on a post it, three things, so you have that ready to go when you get to writing time.
6. Other decisions you can eliminate will help. If you can make a big batch of soup, or buy 60 of the same microwave meal, or lay out your outfits for the week, whatever you can take off your plate for November, do.
7. Don't be a hermit (unless you want to). But really, going out and talking to non-writing people will and maybe seeing some sunlight will not only be good for you, it will be good for your writing. You will see little things out there that inspire you.
Good luck. Writing at any pace is a success, so however many words you get, and whatever you learn about what does and doesn't work for you is good stuff.