I don't do a huge amount of physical activity. I play tennis, I work out sporadically, and I eat well and take care of myself.
Acting is a really simple job - it's just hard to do. You just have to be that person with their background in that situation. That's all it is. My kids do it all the time when they're dressing up and playing games.
Let's face facts, this is visual medium, there's a very high premium put on people who are good-looking. But the minute you rely on that you get yourself in trouble. You certainly don't make a career out of that anymore as an actor.