4. Proper Sleep
Your body needs time to recover from the tax you placed on it during your exercise or athletic event. When your muscles are taxed through exercise or weight lifting, you create micro-tears in the muscle fibers. These micro-tears are good, as they signal muscle rebuilding (which leads to increased strength). It is during your rest and sleep cycle that your body is able to repair these micro-tears, rebuilding your muscle fibers and strength.
Without proper rest, your body is working like an overtaxed furnace, barely able to keep up. Without rest, your exercise or athletic performance will suffer.