Do Something Physical Everyday

The human body was never designed for a sedentary lifestyle. It was created to hunt saber-toothed tigers and walk forty miles a day. When we have no physical outlet, tensions build up within us. The body reacts to minor frustrations, such as somebody cutting us of in traffic, as life-and-death situations. The "fight or flight" mechanism is tripped, adrenaline floods our system, our blood pressure skyrockets. Exercise in general and bodybuilding in particular give us an outlet for these tensions and satisfy the body's need for strenuous activity.

Excerpt from The New Encyclopedia of Modern Bodybuilding
by Arnold Schwarzenegger.