Excellent tips @wes-bryan , @David-Thompson here's a couple more from my experience!
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As Wes pointed out, practice exams are usually a bit harder than the actual exam - you DO NOT need to score 100% in practice exams to be ready for test, I'd personally use about 85% as a number to try to be over. Remember on the real test you will certainly get at least a few wrong and that's FINE - you only need to beat the pass mark 
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As you prepare for an exam, make sure you're doing the right kind of practice - as you get closer to test day I'd recommend focusing more and more on practice questions, and going back to revise areas which you frequently get questions wrong on. Going over training material for areas you're comfortable on isn't a great use of time - try to make sure you're really dialled in on those uncomfortable bits to maximise your return on time invested - especially as you get tired with it (and yes, that always happens I think!)
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If this exam is your first in terms of delivery format you can remove a big part of the stress by getting familiar with the process. Go visit the test centre you're going to, or download the remote proctoring software you'll be using and run the test check in process. This costs nothing and cuts down on the amount of "new" stuff you're managing in one go.
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Finally, remember exam strategies and think about how you're actually going to work through the exam. One big issue I always found was how daunting a long exam feels - but if you start thinking about breaking it down, you can begin to get more of a handle on how you're going to get the thing done. A couple of examples:
With CompTIA you know you're going to have a few simulation questions, these are going to take longer than other questions and can seem like quite a lot to take in. The interface isn't bad, but can seem a bit crowded at times - If you haven't gone over to https://simulation.comptia.org/ to get used to what they're going to look like, this might slow you down, but you're smarter than that right?
On the same issue, in every CompTIA exam I've ever taken, the sims always appear right at the beginning of the exam, so decide - are you going to attempt these first and allow yourself to be comfortable with the fact that you've spent a while on those handful of questions, or would you be more comfortable skipping past them and doing all the multiple choice questions first? That might work - knowing what is more comfortable for you helps!
For those multiple choice questions too, you don't have to answer them in any specific order, CompTIA let you mark questions for review, skip back and forward etc. Perhaps take out all of the easy questions, then come back to the harder ones?
I think having a plan about how you're going to approach some of the aspects of the exam up front can really help reduce anxiety - or at least reduce the number of things to be anxious about!
Good luck!
