Make time to exercise. It does not have to be hardcore, but developing some muscle mass and tone will really help. And before you say you are too old: we have some older folks, well into their 70s or even older, that still rock the gym. The main cause of weakness and loss of both muscle and bone as we age is a lack of weight bearing exercise. A thorough checkup, some research on exercise physiology, and a little time to find a decent gym with a trainer who has a clue will pay off. The first step to dying is to quit living.
A lot of things you could do more or less with body weight - pushups, dips, chins. A lot of walking with the dog will continue to provide benefits. If you can stand to swim, do that - I swim like a brick and am very uncomfortable in the water, but it is low impact and can be good stuff. My Dad grew up in the Depression and like many then had a crummy period, but he started running at 40. He had chest pains instead of the big one at 65, and lived a good life until he did have The Big One at 75.
I survived a really sucky medication reaction a few years ago (at 48) and all the crud that came with it, largely because I have tried to stay active and in decent shape. People who know more than I tell me that 95+% of those who went through what I experienced would have croaked; I was inconvenienced. I'll admit that my favorite chiropractor and his staff of massage terrorists see me a lot, but it's worth it. Other than the gray, I can pass for a lot younger, and I do better than most my age. I worked nights for a long time, and I HATE getting up in the morning. I try to get up at 4 a few days a week so I can get to the gym and do various things (cardio some days, weights others); sometimes I got after work, but either way, it is worth it in terms of quality of life. There are too many worthless buggers who would be gratified if I croaked, and I want to be a pain in their backsides as long as possible.