I think your fear is healthy if it motivates you to fight the effects of aging. I know many people in their 60s and 70s and it's amazing the effect lifestyle has on where you end up. I know 60-year-olds who are senile and frail after a liftime of recreational drinking, poor eating, and inactivity. I also know 80-year-olds who are sharp as me, learning new things, and biking, hiking, or running more than ever to stay young. My 70-year-old mother just got her PhD and teaches nursing thanks to a liftime of healthy eating and intense exercise. Those are the seniors I think of when I go to the gym and choose salad over my craving for burgers and fries when out to eat.