Both my father and my father-in-law became less active because their health was not as good as it once was. It was all downhill from there.
In my opinion, you need to become more active, not less. I am 76 and dealing with various health challenges. So I run and walk for 10 to 20 minutes every morning before breakfast. I won't give that up unless I can't do it anymore.
Nor will I give up on RVing unless I can't do it anymore. On a recent RV trip, my wife and I took a shuttle bus in the town where we were visiting. A fellow with a walker and an oxygen tank stumbled his way onto the bus. And I said to my wife, "If he can still get out and about, I certainly can too."
If you're not active and want to be, start with the easiest thing you can do and increase it from there. Try walking. It doesn't have to hurt. If it does, start with less. Don't believe the old fallacy, "No pain, no gain."
Good luck.