I'm "only" 52 (almost 53) and I'm doing things now I didn't do in my 20's. I've had injuries and my recovery time isn't what it used to be. I have to work harder to stay fit. But the years have given me mental toughness I didn't have when I was young and that makes up for much of what I've lost physically. I'm still outracing guys who could be my son.
I'd sooner mow the hill down than go over it!!!!
IMO it's all in your state of mind.
If you only travel on sunny days you will never reach your destination.*
* May not apply at certain latitudes in Canada and elsewhere.