I just sort of… lost momentum over about ten years. Arthritis advanced to the point I sold my motorcycle because it sucked to ride. My workdays got shorter and shorter because I couldn’t stay on my feet, until finally I shut my business down. I wound up retiring a lot earlier than I expected, because I wasn’t mobile enough to do much of anything.
The majority of it turned out fo be various food allergies. I’d been on meds to deal with that for most of my life; those meds, in turn, had their own side effects. It was a nasty positive-feedback cycle. Memento persuaded me to try keto. That got me out of the loop, and far enough ahead I could start exercising a doing mobility work.
The point of the rambling is that this shit will creep up on you bit by bit. You’ll be dealing successfully with each day’s requirements, and then something trivial will come up and you just don’t have any gas in the tank to deal with anything extra, no matter how small.
A friend of mine got off work one day, drove home, and couldn’t make it up the steps to his house. He didn’t feel bad, he was just "out of go." After a while he had rested enough to crawl up the steps. He called his doctor’s office the next morning after telling his employer he’d be off for a few days. He never made it back; it turned out he had Stage 3 lung cancer. He had never felt weak or short of breath, until one day he needed a little extra oomph and it wasn’t there.
Overwork isn’t lung cancer, but it can still be debilitating. And long-term debilitation can take a long time to recover from. Don’t be That Guy.