Maybe I don't know yet how to be happy and play well at the same time.

When you chase perfection, when you make perfection the ultimate goal, do you know what you’re doing? You’re chasing something that doesn’t exist. You’re making everyone around you miserable.
You’re making yourself miserable. Perfection? There’s about five times a year you wake up perfect, when you can’t lose to anybody, but it’s not those five times a year that make a tennis player. Or a human being, for that matter. It’s the other times. It’s all about your head, man.
-Brad Gilbert

Tennis is the loneliest sport