Since I tore a tendon in my right ring finger playing basketball several years ago I made a conscious decision to avoid playing strenuous sports, especially any with significant physical contact. Some may consider this to be wimpy, but it seems like a reasonable decision to me considering the life-altering injuries many of my friends have sustained because of their sports activities in high school and beyond.
My friends are not high-level athletes like Kevin Everett, but their collective inventory of broken bones, torn muscles, back problems, knee problems, ankle problems, and messed up fingers convinced me that playing sports isn't generally a worthwhile endeavor. I've got friends in their 20s who can't lift their arms over their head without pain and who can't walk a mile without knee braces, all because they like tossing balls around. No thanks!
My knees are stressed from running for a decade, but I stopped that and bought an elliptical machine instead. I love it, and it's easy on my joints. I also work out with free weights, but I avoid quick movements or anything likely to cause injuries. I'd like my body to stay usable and healthy into my old age!
As a corollary, I've got a lot of respect for Tiki Barber's retirement from the NFL. It takes a lot of willpower to change direction in life, especially when the costs and rewards of your current position are so high. However, Mr. Barber recognized what football was doing to his body and decided he'd like to leave while he was still intact. Smart man.