I turned 50 last week. There's a lot of significance attached to that, whether we like it or not. When you turn 40 you figure that, roughly speaking, you've reached the approximate halfway point of your life. Add another decade to that and, on average, most people will be past their halfway point.
Of course there are exceptions. My paternal grandmother lived to 90 and her mother lived to her mid-90s, so genetically I have some longevity in my favor. But the odds are also much higher that one's quality of life in the "second half" will be worse than the first. It's hard not to start taking stock of one's health, and all the things that could go wrong.
I don't smoke and I drink responsibly and in moderation. My blood pressure is reasonably low, my cholesterol numbers are decent (but could be better), and I don't have arthritis or any bad joints (yet). On the other hand, I am lazy and don't exercise. I am slightly overweight, though my weight has been stable for nearly a decade. My father developed diabetes in adulthood, as did his mother, so I have to watch out for that possibility, but I don't have the greatest diet and I snack a lot.
I'm at much higher risk for skin cancer than the average person, so I have to be vigilant and see a dermatologist twice a year. (I hate heat and humidity, so not going outside isn't a problem for me.) Both my grandfathers died of lung cancer; as a child both my parents smoked and I was exposed to a lot of secondhand smoke, before anyone realized how harmful that is.
I could arrange these things on a board in pro and con fashion, to see the bigger picture. My lack of physical activity will probably end up affecting my quality of life in twenty years or so in terms of mobility, and may also put me at higher risk for heart disease. This is serious, and I know I should do something about it.
But today, right now, I feel good. I have minor issues, but overall my health is good. I know people who have had hip replacements before reaching 50, and thankfully I haven't had to deal with anything like that. It's somewhat true that age is not a number but a state of mind; there are things we can't control, and things we can.
Part of me wants to see what would happen if I just kept going the way I am, without making the effort to exercise, but it's not like I'd get a do-over. I guess it's time for me to think about taking better care of myself.