Hey now! 
Had a weird experience skiing in March. As I go about my usual life, I’m pretty confident I’m in the top 10% among my age group in terms of fitness. But out on the mountain, a HUGE number of the instructors were in their 70s. I think I saw maybe 2 skiers whom I would describe as obese. And MANY who were older than I. And I was way at the bottom in terms of skiing ability. Just weird to put yourself among such a different cohort.
(Funny, but in our lodge there was this one really old guy. He was INCREDIBLY fit. Way more muscle mass than you expect in a guy in his 70s or older. But EVERY TIME I saw him, he was wearing a tight sleevelss muscle shirt, and those silky short-short running shorts. I wanted to tell him, “Dude, you’re CLEARLY in phenomenal shape. But you are also a little old man. Put a shirt on!”). 
I often look at overweight men my age and wonder how the heck they mow their lawn. Or even tie their shoes? (They probably wear slip-ons.) Not to mention keep up with their grandkids (probably my biggest single motivator these days. They wear me out!)
I intentionally changed my mindset from “improvement” to “maintenance.” The first time I realized I was doing it was when I started swimming maybe 5-7 years ago. When I used to run and lift, my thinking was always “run faster/further, lift more, get stronger”). And when I started swmming, it kicked my ass, so I was only doing a few laps at a time. I gradually increased the # of laps I did until I was up to IIRC 70+. But swimming that many laps took quite a bit of time, and I found myself looking for excuses to NOT go and swim that long. So I dropped it down to 32 laps, which I did 3x a week without fail. It fit into my schedule and I was able to keep it up (until covid. Gotta see about getting back into that!)
Same thing with my pushups and situps. I was increasing both week by week, until I realized the same mindset was creeping in - I was trying to convince myself to skip days. So now I just do 2 sets of 12 pushups, and 8 sets of 15 different crunches every other day without fail. Only takes me 5 minutes, and even I am not lazy enough to say I can’t do 5 minutes every other day.
I bike 20-35 miles with my sister about 3x a week. Maybe 5 years ago we stretched it and rode a century. But we both realize we don’t need to do that again. So we are content with urging each other to go 3x each week - and modestly pushing each other during our rides.
I was always that guy. I wanted to think of my body as something that could bear any amount of stress. As a result, I probably am paying for that attitude these days.