As I get older, the "were" thing is getting to be more the case. Especially in grappling. Joint issues, ya know. So it's getting to be "Do as I say, not as I do". Too bad.
You and I are about the same age, Jobo (I'm 62), but age can affect each of us differently. In my early fifties, Like you, I was still in great shape and kept it up until pretty recently --especially my conditioning. I thought I could hold on for decades! But, in the last couple of years, injuries (back, knees, ankles) have made it painful just to be on my feet for too long, much less run. And, without the cardio, my weight has gone up some too.
I can still do our forms and drills, kick, punch, and spar a bit. But the other night when I tried to shoot-in on a student to show him that his "anti-grappling" take-down defenses were garbage, my knees and back really suffered ...and my technique was terrible (still slammed him on the floor though). And the next day the pain taught me that I can't keep doing that.
Does that mean I have to give up coaching and close down my club? I hope not.

...Maybe if I can recruit some young wrestlers who can help me out?