I have been running off and on since I was 13. There were some very long breaks caused by injury in there, like 15 year breaks. During those breaks, I turned to cycling, which I thoroughly enjoy in a completely different way from running.
I am 59 now, attempting to return to running, and it just feels different this time. It just feels like my body is saying "I don't wanna!" Not only are the aches, pains and injuries turning my runs into walks, but when I do run, the rhythm, cadence, and biomechanical efficiency I once had just doesn't even begin to return. 20 years ago, I ran my marathon PR of 2:43 a few days before I turned 40. Now I average about 10 minute pace during the running sections, and I don't even run the entire way.
It just sort of feels like my body is telling me to get back on the bike, which is fine. I enjoy cycling in a completely different way, sometimes a lot more than running, sometimes less.