This is the world's toughest question.
For me, I realized in my 30s that tennis was just a game, and that I'd played thousands of games of tennis. It's hard to have the same "gotta kill" thing that you do when you're younger and just getting into the sport.
At the same time, it's simply more enjoyable to win than lose. But I can't crush myself over a loss anymore; I might've done this back when I was 19.
I suppose much of this rests on how a person views himself: is tennis his one Big Kahuna? or is there a lot of different things he prides himself on being able to do reasonably well?
There is also a category of competition known as a "good loss": one of my best games ended very closely. I lost, but I know I played some of my best tennis in that one match, so I felt pretty good about seeing that come out of it. But would've been nicer to have won the damn thing.
To Praise, To Bless, To Preach--the Dominican Order