That's not unusual. A longtime friend finally retired at around age 75 after decades of teaching and various seasonal side jobs and volunteer work. It was really hard on her and after a couple of years she resumed doing some volunteer work.
My dad died soon after retiring from the university where he'd spent a career, also around age 75, although in his case it was a relapse of prostate cancer. Still, prostate cancer is generally well controlled with good health care, and his had been under control for more than a decade. He seemed to prefer working and I wondered whether retiring hastened his demise by depriving him of something that had been a huge part of his life for decades. He loved to talk about work, especially the Machiavellian machinations of big university politics, and enjoyed his role as a sort of Sir Humphrey (if you've watched the Britcom "Yes, Minister," that role played by Nigel Hawthorne was the English version of my dad).
I was forced to retire early on disability after being hit by cars twice in less than 20 years, with serious neck, back and shoulder injuries, compounded by cancer. It was a bit of a shock at first but, TBH, I enjoy it now and have little desire to resume even part-time work. Although I'd need to find some form of self-employment, as I doubt I could find a part-time job that could accommodate me.
I even had to give up cycling last autumn after neck pain from old injuries became too much (along with COVID-like symptoms that persisted for months, despite the vaccines). That was frustrating for awhile. But I switched to running on good days, jogging on not so good days, and walking when nothing else worked. So I'm still reasonably physically active, getting out of the house, into the sunlight when it's around, eating well, etc.
Yeah, there's a temptation to dwell on the past. Been there. But whenever I do mull over the possibilities and complicated alternate outcomes, I realize there's almost nothing I'd want to relive or try to "get right" a second time. If I'm brutally honest with myself, most things that didn't turn out well were because I was an idiot. There's no guarantee that given a second chance I wouldn't be the same idiot, or worse. Possibly the only action I might consider for a do-over would be my first marriage. I doubt there would be any harm in skipping that huge mistake if I had a chance at a mulligan.