I took my first exam last year. Having skipped G1 and 2, I was totally nervous. My fingers were so numb and were moving automatically while playing the scales. Luckily there weren't any mistakes made
It is alright to repeat if you are so nervous and don't know what you're playing anymore. I had to repeat for my first piece as my fingerings were all wrong. I took a deep breath for every scale and piece I had to play, and it worked.
Act calm and remember to smile! Good luck!