I am 69, I did 3 years of Tae Kwon Do in the mid 80s, had to quit due to back injury from all the high kick. But I never stop practicing at home. I have two heavy bags and still working on them every week, never stop. I also do weight training. I am still putting in about 7 hours a week in exercising.
That said, I felt good, still strong.................Until like 65. BUT then, I do get weaker even though I try very hard. Injuries start kicking in. I definitely not as strong as 10 years ago. I am not that strong nor very talent in MA, I just never stop trying. 10 years ago, I could bench 2 to 3 reps of 225lbs, 2 years ago, I could only do 7reps of 185lbs. I since working out at home due to shutting down, so I cannot gauge.
No, I don't feel just as good and just as strong as I get old. 65 seems to be a magic number, I never had knee problem, after 65, one day when I walked down the stairs, my knee buckled and almost fell down the stairs. I since has knee problem that I never injury before, just out in the blue.
I still push in weights, I still wear two weight jackets total of 72lbs to do pushups at home as bench press, 4 sets total with 20, 18, 13 and 10 reps (less reps from set to set) once a week. But I doubt I can do 7 reps of 185lbs as free weight bench press is harder.
NO, there's nothing good about getting old. I try, I really try. My speed gets slower also. Maybe that's just me, but I have suspicion that a lot of older people are fooling themselves to feel good. Yes, I can easily out muscle and fight ordinary people that are in the 40s, but come on, compare to a young person that is in shape and trained....................? Yes, I do look quite a bit younger............for my age. But trying to compare to even to a 45? I am not going to kid myself.
BUT, I am not giving up, still do exercise, my goal is to be mobile when I get old, I also exercise my brain, designing very high end hifi power amps, just learn C++ programming from a book cover to cover last year. Going to learn Python programming with my grand daughter this summer. Just got my 3rd US patent in electronics design from a contract work in 2016. Retirement is as busy as ever.