Work out with your friends.
"There was a time at the initial end of my career at 33 when I was not training very much and I realized pretty soon that working out needed to be a regular part of my life," McEnroe says. "So I'm still someone who likes to work out five or six days a week. I think it makes me a better person and helps me think more clearly." Unlike a lot of pros at his stature, however, McEnroe says that he finds pleasure and inspiration in bringing others into his regimen, be it a trainer, friends (Laird Hamilton and Chris Chelios are among his frequent workout buddies), or his wife, Patty Smyth. "I prefer to work out with other people, as you push each other."