I think Rollo has some excellent advice. When you're playing someone not as good as you, use it as an opportunity to work on those parts of your game that are subpar. For example, I'm a baseliner by nature. When I'm playing someone I should beat without too many problems (not too often these days because I'm in an excellent league!), I do thinks I would not normally do. I'll serve and volley on several points and look for any opportunity to get to the net if I have a short ball. When I'm not as certain of the situation, I tend to retreat to the baseline after retrieving a midcourt shot. Also, look at it as an opportunity to work on the mental side of your game (most important!). The key is to relax and not worry too much about it, and not to think that you're better than you are. Unless you're overwhelmingly better than your opponent, it's not unexpected to have a reasonably close 6-4, 6-4 match. The difference is usually how you play the big points. Good luck and have fun!