I used to run. I was never a very graceful or fast or accomplished runner, but I did it. I ran a marathon once and a few shorter races. But mainly I knocked out a few miles at a time at a slow but consistent pace.

Most of the time, I didn’t really like running. I felt like I should do it because I was trying to be healthy and stay fit. And if I’m really honest, because I was always trying to lose ten pounds. I didn’t do it just for the love of pounding along the sidewalk.

But then, surprisingly, sometimes I did love it. There were certain days when the sun was out and it just felt great to be moving. Or I’d take a long run with a friend and use it as a chance to finally have an hour-long uninterrupted conversation. Sometimes there was a beautiful view that I wouldn’t have seen from a car. Or a neighborhood that I wouldn’t have found.

As of a couple of years ago, I can’t run. If I set off at a jog, it doesn’t take long for my right leg to start getting tired, and my gait becomes completely off balance. If I sprint, that happens almost immediately. Falling and busting my knees again is a certainty. And in terms of exercise, walking is actually better for me. If I walk quickly, I can get my heart rate up and keep it up for longer. So I don’t run anymore — I’m retired.

I’m surprised at how much this bothers me. Not all the time – some days I’m actually glad to have an excuse not to be struggling into a sports bra. But from time to time, there are days when I’m crushed that I can’t run. I miss that feeling of strength and freedom. I want it back. I want to win a race with John. I want Tom go jogging with me. I’m sad about what I’ve lost, and scared about what might follow. I worry that I’ve gone too gently into this sedentary night. It’s not the worst thing in the world – plenty of people have a lot more to worry about than I do. But it’s still tough.