It has a lot to do with psyche. If you have anxiety, it is entirely possible to even fail the most basic questions. And unfortunately, you can't just say "Sorry, I'm having a panic attack. Could we do this tomorrow?".

I think the best course is anxiety management. But unfortunately, some people get dependent on drugs just to calm their nerves before something important. I know people that can't hold meetings or presentations without taking beta-blockers and the likes.