>>16725548 (OP)i failed 1 test by like 2-3% because i changed my test-taking strategy from a tried-and-true method to one a professor recommended. just had to study a little more and use my old method for questions i was slightly unsure on, but my confidence wasn't really hurt since it was obvious what i needed to do.
other test i failed was my national licensing practical exam which cost $1500 itself and had to fly across the country to take. going into it the second time i had even worse confidence than i had the first time since i failed, but managed to pass it easily. partially because i practiced the skills a little more and made sure to follow their exact format to a T, mostly because everyone that took it the first time in the same month i originally did failed and 95% of people who took it after that month passed.
only real advice i can give is study longer and more effectively, ensure you know EXACTLY what the testing will look like and what they're looking for (which you now know since you took the test for the first time), modify your test-taking strategies, and hope for the best.