A solid preflight inspection calms me down prior to departure. Try to have a look at everything and anything that may compromise your fun time before you take flight.
Check the aircraft thoroughly and radio programming.
I inspect the runway for foreign objects, holes, mole hills, etc.
Have a flight plan including approximate speeds, altitudes, attitudes and flight times.
Check your environment (sun location, wind).
DON'T RUSH YOUR PREFLIGHT! Remove all doubt about your equipment and environment before you get airborne.
I avoid crowded skies. In my early years, I avoided crowds altogether. I was nervous someone would watch me crash. Since then, all the people I was worried about watching me deploy a lawn dart...already did it themselves.
Try not to worry about anyone or anything while flying. Once you spend enough time with your equipment, it will become an extension of you. PRACTICE, PRACTICE, PRACTICE.
Flight simulation and lower cost aircraft may also help keep you calm.
Everyone is different. Maybe you only need to avoid coffee for the day
Clear skies and the best of luck!
-PD