I practice, I take lessons, I read and learn all I can to play better - but at match time - I JUST PLAY!
The less attachment that I have to winning the match - the more fluid my shots become. Instead of feeling like "I have to" - I instead well up with gratitude for being able to play and I feel more like "I get to" (play tennis). When I have this peaceful bliss of appreciation flowing through my veins - then and only then am I IN FLOW - in the zone - playing with all my heart and very little of my mind. My body knows what to do.
Relax and play!