When I was in my twenties, from time to time someone would ask me in the gym why I was working out. I'd always reply, "I'm preparing for old age." I've also been fortunate not to have had much interest in alcohol, and no interest in smoking or narcotics. I've always consumed a healthy diet (all home cooking except when traveling) based on a proper understanding of what obligate omnivores like us need - no interest here in faddy silly diets that hurt and harm.

As a result, I'm nearing 64 and can still out-perform most people a third of my age. I wake without aches and pains, I have no physiological constraints, and I sleep reasonably well for someone who's been plagued with insomnia since early childhood. I'll exit in my 70s because I have no interest in decaying like ordinary people, but up to that point I'll feel great - simply because I have always made adequate lifestyle choices and prioritized my health, both physical and mental.