Well, I've never taken this particular tests, but I've done lots of make-or-break exams, job interviews, and such. Here's my advice:
1. Self talk is extremely important. Tell yourself that you can do it, that you WILL do it, even if your heart doesn't completely believe it. You say you've passed every test and exam leading up to this. That means you've worked hard, you've learned the stuff, and you're prepared. Remind yourself of that. Say it out loud. Ask your friends/family to remind you of that, just so you're hearing it from somebody else.
In fact, I'll say it. You've worked hard. You're prepared. You've got this.
2. Relax. I know, that's stupid advice, and there is nothing less relaxing than someone commanding your to relax. ha ha But it's OK to take a break before the test. Doing that will probably help you more than any last-minute cramming you might do. You know the stuff. Your brain is full. What you need now is to have a brain that's well-rested and alert. So, take some deep breaths. Go for some walks. Have some fun. You've go this. (See point #1 again)
3. Be kind to yourself. You're going to get stuff wrong sometimes, so make peace with that possibility. Here's some good news: I just googled the NREMT (I've thought about getting that certification at various times, and you got me curious). Guess what? If you fail, you receive specific feedback, then you get to take it again. And again. And if you fail it the third time, you can take a refresher course then try again. So, don't put too much pressure on this. Just remember, the worst case scenario is that you have to try a few times before you get it right. And that really ain't that bad. So, give yourself a break. Give yourself permission to make mistakes. Ironically, that attitude will give you the best chance of success.
Here's the thing, and I know some of our other older members will back me up on this: These make or break moments really aren't. You'll be OK, no matter what happens. And while humble pie can be a tough dish to swallow, it isn't the end of the world, or of anything else.
Rooting for you--
T