If you're lucky, you will always have some nervousness when you fly. Professional entertainers will tell you they always have a bit of stage fright before performing. Flying an RC model is one of the most mentally draining things we can do. In time we get more acclimated and it doesn't seem as prevalent as earlier. Stepping up the complexity or investment (time or money spent) renews the jitters for me. When testing a new model, I find it helps me to spend some time thinking out my sequence of events before the flight. I think there is less pressure if you always know what you want to do next.
I had a professional musician once tell me that eating a banana just prior to a performance always tends to lessen the jitters. I don't know if it was putting some solid food in your tummy, blood/sugar balance, or if the content actually made a difference but it always helped me. When I used to compete, I would keep some bananas in my cooler for use just prior to my flights. Even if it doesn't work for you, bananas are a good wholesome food. Can't hurt.