Simple is difficult. I like some of the suggestions here, re diet, walking, building strength, getting legal stuff into trusts or joint ownership, etc. but let me say this:

I am 75 and some of this is scary. I AM that old parent. I live alone post divorce in the boondocks (Sierra Foothills) and thought that friends would flock to my place. Wrong. It is beautiful and I take fabulous photos without leaving the property, but all my friends are 50 miles away, the Bay is 150 miles away, and family is spread out. Good friends are essential. Loneliness is a killer of older people. I may actually move this year.

Next stop (hint, hint ) I am going to get a new bed and mattress, and lazy boy. Couches and cheap chairs are back killers.

I also suggest having someone clean now and then, and a handy-person nearby for minor things, and also to find professionals when something major needs work. This extends to health. A sharp friend might spot some minor problem that isn’t minor.

I do get out and work out with the chainsaws. Heck, trees fall in the storms. This is not for everyone. Nor is climbing. I live on a ridge and everything’s a climb. Can’t complain about the exercise. Walking is great. I’ll use the elliptical that I used when we lived in flatland when I move. Family got me an Apple watch, which nags me to move, stand and exercise. Exercise doesn’t really count until you punch “Workout”.

Mentally, I have no TV. That’s a big win for sanity. I love classical music and play as much and as well as I can. Music is great for the mind and nerves. Playing is a challenge for the brain and motor circuits. Puzzles are good. I have been an amateur photographer for over 50 years. If I’m not wandering around the property, grabbing sunrises and sunsets, I do get out, and plan to get out more. Driving is a PITA for seniors (not all of them) so a small group photo outing is great and I plan to do so when there are people nearby to recruit. Phones have popularized (good) and also trivialized (bad) photography. But it’s a challenge to stand out from the ordinary selfie world.

A big vote for strength exercises. Muscles protect joints. Period.

A second boost for getting some help now and then. When my daughter visited, she did a lot of cleaning and straightening up that gave me a head start in my attempts to single-handedly create some order out of chaos. Much appreciated. Also, I’d really like to give away some excess items, but she lives in a tiny condo, which is frustrating. If folks mention unused items, offer to take the items away for them.

I’d garden but deer eat everything here outside of a 7 foot fence, and gophers and rabbits get the rest. I used to grow roses and a few veggies. Gardening (when it’s not warfare) is a great hobby. My grandfather came from the old country and had a big garden, so I’ve been doing it almost all my life.

Encourage! Visit. Get friends to visit. If they’re old like me, they probably grew up in the 60’s. Bring brownies. Bring good food or somehow have it sent, that’s out of the ordinary good or a pain to make. One way to help oneself is to help others. If I weren’t so isolated, I’d be repairing things for other seniors. A friend was transitioning off SLR’s and is batshit happy that I showed off and recommended my mirrorless camera. Seeing for real and chatting with others and helping them is a way to get one’s own troubles off the front burner onto the back burner.

Find old photos, or have them find and catalog them. Helps with memory. I scanned all the old photos my parents had collected. I have no problem with memory, except short-term, so I got a bunch of air-tags to go along with the Apple Watch my family bought me for my birthday (nice!) My mind just gets overloaded by reading Hacker News, of course.

And if they’re not computer-savvy, offer some help. On my “other than HN” haunt, I offer help whenever I can. It’s a good feeling. (Karma instead of paycheck, oh well). HTH.