Second, when you get deep into a match I find it's also like a form of meditation because you are so focused on one task that everything else falls away. When this happens we reach the “flow” state described by Mihalyi Csikszentmihalyi in Flow: The Psychology of Optimal Experience.
Third, one of my main goals in life is to find balance. In tennis it's integrating the mental challenges with the various physical challenges. Trying to find the right blend of power, touch, spin, tactics and even deception (by setting up to make it look like I'm going one way then going another at the last instant). Then there are the various challenges. How to handle a power hitter? How to handle a much younger player? How to pace yourself in a 2+ hour match in 90+ degree heat? How to play with an injury? How to play when your game is "off"? And how to handle a loss? I think a lot of this spills over into other parts of life.