No matter what exams you're doing, no matter how many exams you have and no matter who you are, I wish you good luck with all of your exams. I know what it's like to go through the exam period, I've already been through it once with my GCSEs. For me, this exam period is my second - and it certainly isn't my last, and it probably isn't your last either. So, anyway, below is one of the things I have been saying to someone, who shall not be named, who has been constantly worrying about a particular exam.
Walk into the exam and, in your head obviously - don't want to be disqualified -, say to yourself "I am going to do my best, whatever grade I get on results day, I am going to do my best". Say that and it'll put you in a positive state of mind for the start of the exam, and boost your self esteem during the exam. I didn't do this last time, and while I passed with 7 Cs and 3 Bs, I couldn't take the subjects that I wanted to take at sixth form. So, what did a friend of mine say on results day, well, something very similar to that. I'm not going to give you the exact words he said, but it was along the lines of "Be proud, you've done your best, while you may not have met the criteria for the course, you have gained skills and knowledge along the way, I am proud of you". What he said is basically what I have said above, but he said it after the exams - so a past tense "do your best".