It is a fact that as we get older we start to loose it. But don,t use that as an excuse to not do things. Lower your expectations and enjoy being out. I ride most weekends unless I have some other hobby going on. I have discovered bikepacking this year. I go at my own at my pace and my distance. I plan it to be flexible so if I,ve had enough I can stop. Tomorrow I will be out celebrating Global Fatbike day with 30 or so others in the wonderful Forest of Dean. Its not a race! and thats the point. It,s an experience to be enjoyed on your own or with others. I dont do Strava or anything like that. My rides are measured in fun. I am 67 and have never been fast, super skilled or any kind of athlete but it,s still good fun.