What's your best studying tip/advice?

I have the exam of my life in Jan. and I’m so scared that just thinking about it makes me want to pee and barf. I would super appreciate any advice you have for studying whatsoever.

My background:
I’ve never been a great test taker, maybe only so-so. I’ve had a long break between originally learning the material and taking the test. I have a hard time staying focused when I study. The material is mostly anatomy and physiology with some business ethics and massage technique. It’s for national certification in massage therapy.

I will be so grateful for any info that will help me not die.