I used to be an epic walker. Every Saturday night between 2006 and 2007 I would walk from my friend's home East Central Seoul to my apartment in the North end. It was a straight line and it passed through a lot of interesting neighborhoods. In Japan I'd grab my bike and see what was happening up in the mountains.
Now I have trouble getting in and out of bed because of Sciatica caused by Spinal Stenosis. A two hour walk anywhere just isn't doable anymore. Hitting the gym or having a jog is a no-go.
My advice is to try to die before you get old.