Well.. of course 比賽 is 好緊張, just talk to yourself... win or loose is not matter, just enjoy the process of 比賽. As I am a flute player and I have 比賽 all the time before, I just chew gum and drink some hot tea.... that is what I do... also.... try not to think about win or loose and if your 比賽 is on a stage... just pretend no one is there and play as you were practicing.... worry too much will not help....