I'm almost 50 and even with regular exercise ... things are still not easy. You have to maintain a certain level of activity and if you just get off one or two days, it will take you a week to jump back to the same level again. A year ago, I got excited and went running around with my little nieces and nephews for a game of lazer tag. I did shuttle running without thinking for about an hour. I thought I did great, everyone thought I was in great shape and an athlete ... I felt like I was 18 again. I couldn't move out of bed the next morning and my muscles cramped up for two or three days after ... it took me a couple of weeks to get back to normal. Enjoy what you have ... the end, beginning of the end or the ending is closer than you think.