How do I deal with nerves?

I am new to Masters swimming, and I am swimming my first meet at Auburn this weekend. Today when I was practicing, I would get on the blocks and start thinking about the meet. I would get so nervous and shaky that I could barely finish a 50!! After I stopped timing myself and told myself I was "just swimming an easy 50" I did okay. Any advice for Saturday? Also...I cannot decide about my flip turn. I feel like it is different EVERY time I do it. Sometimes too close, others too far away, and sometimes right on. Should I try it in the meet, or just go for the open turn? It's not like I'm a contender or anything..... Thanks for any advice!