My martial arts instructor always said "You don't grow old from the years; you grow old from inactivity".
The sign at the entrance to our city park states, "You don't stop playing because you get old. You get old because you stop playing".
There's a lot of truth to that, I think. I was in fantastic shape until right before I turned 30. I needed a bunch of back surgeries and stopped working out. Then I never felt well enough to start again. Of course the pages kept coming off of the calendar and then I had some other medical issues as time went on. I finally got sick of it back in June of this year and have been pushing hard to get back into shape ever since. I dropped 55 lbs. since June and just did 10K this morning in a little under 50 minutes (best time yet this year), and did another 3.4 miles after that. I'm doubtful I'll ever have the muscle mass I did. Or the speed. But I'm not 30, or even 40 anymore. Regardless, I feel a hell of a lot better than I did a year ago.
There's a skateboarding quote that is probably ripped off from that:
"you didn't stop skateboarding because you got old, you got old because you stopped skateboarding."
I'm 41 and still boarding, admittedly I'm not throwing myself down nine sets like I used to, but I still love it.