Generally, after about 40, shit takes longer to recover from, and your lower back will start to hurt if you have done much physical labor in your life. You will be able to remember all your more serious injuries easily, because they give you a little twinge now and then.
So far that's about it [pauses and knocks wood]. i haven't had any health problems at all, except i am more prone to saddle-sores from cycling. I think this is because my black pubic hair was replaced with mostly grey ones [yes this happens], and they are much stiffer and much longer than the old version. So i have to give my balls and taint a #2 [skinhead haircut] before cycling, and keep plenty of hydrocortisone ointment on hand.
I cycle and do tai chi year round, and do a lot of landscaping/gardening work in warm months, but have never in my life engaged in any kind of voluntary exercise that i did not get paid for, until i bought property. i eat what tastes good, and haven't seen a doctor (except for this infection i got after i wore dress shoes with a broken toe) in 11 years. There are times when i will go like an entire hour without thinking of sex, which never happened til maybe my mid-50s.
So i have to say, getting older really isn't that bad so far. Most of my friends are dead, from drugs, alcohol, and murder, and that sucks (and now they're statring to go from old people shit). I have high hopes for a couple of my older enemies dropping dead with this COVID-19 shit, and regularly google their names with obituary, but so far no luck.