When I went for my first exam in many years, I was nervous too. After I got into the feel of my pieces, I completely (well almost) forgot that the examiner was there, and just concentrated on the music. I lost myself in it, and I heard everything as it should be. I stuffed up a few times, but still passed with an pretty good mark.
You'll be fine. Don't stress yourself out too much, and don't get so nervous that you will freeze up, if you do that, then you will be in trouble.
As many people have said, being nervous is natural, if you weren't nervous, I'd be surprised. The trick is to keep it under control, and once your in there and playing, quit worrying, because even if you do stuff up, worrying wont prevent it.
Good luck Harris!