How do you get over the fear of tryouts?

On Monday, I have tennis tryouts. I am pretty good, I can hit the tennis ball, do forehand, backhand, topspin, but there are a few things to work on. However, I feel like I will do really bad when I actually perform at tryouts. To add on, in 7th grade, I failed the basketball team, and last year, I failed a singing contest. As a result, I don’t have a lot of self-confidence. This year, I need to get in! We’ve paid $300 for equipment, lessons, etc. As a result, my mom will not be happy if I don’t make it. Any tips on how to get rid of nervousness? Tennis skill tips, advice?