Taking good care of yourself can give you some really good feelings. When you eat well and move, you plug yourself into life. That means the joy of learning, experiencing new things, getting enough rest, playing, sharing with friends and family, working hard and then relaxing, and knowing you've done your best.
Compare that with what happens when you don't take good care of yourself. You feel stuffed and tired, you don't look your best, you feel sickly or actually get sick more often. You age more rapidly than necessary. You subject yourself to an early death. You worry your family, friends, and co-workers. And, you feel bad about yourself to boot.