I've been really fit all my adult life - the events of the last year and a half or so caring for my Dad and all that went with it have aged me some for sure. I can still do all the stuff I used to do when I was in my 20's, but there is typically longer rest periods before I do it again.
Several times this summer I'd go out and do a hard 40 miles on my bike, come back to the studio, get something to eat and go walk and carry 18 at the golf course. That's pretty good for 56 year old, but again, the next day the only exercise would be walking the course.
So, like Bob, I think I'm still 25 until the day after