I think it's important to remember that you can never be 100% prepared for any exam. One of the aims of an exam is to take you out of your 'comfort zone' in order to find the limit of your current ability. There will always be surprises and difficult questions; otherwise everyone would get full marks.
So, don't worry if there are topics that you haven't studied, or words that you don't understand, and try not to get too nervous or frustrated. Just keep working hard, do your best, and try to enjoy the challenge of the exam!
I'm sorry if you posted a "comment" and I haven't answered it. I try to answer a few questions here and there, but I'm afraid it's impossible for me to reply to everyone.