This is #5 in a series of essays on aging.

Let me not sugarcoat this: aging brings loss. Losses big and small, but continuous and unrelenting. They are not necessarily the focus of our lives as older people, but they are the backdrop of everything. You cannot talk about aging without accounting for loss.

The foundation of all other losses is loss in the body. Bodily incapacities set off others, like a landslide tipped into motion by a single rock.

Loss is always accompanied by denial, and never more acutely than in the case of your body. Think of the common sayings about aging:

People want to believe that they can overcome aging if they think the right thoughts. Stay cheerful, stay active, remain enthusiastic, join a yoga class and age will never get you.

But it will. Age is more than a number. It’s not a feeling that can be overcome by a good attitude. Your body will gradually (or suddenly) lose its capacity. Your balance will become poor. You won’t be able to run anything like fast. Your skin will grow less plastic and more vulnerable to wounds. Lung capacity will diminish. So will strength. There is a very good chance that you will experience disabling hearing loss. (About half of adults over 75 do.)

Some people’s bodies show the effects of aging sooner and more dramatically than others. Sickness plays a big part. So do diet and exercise. Undoubtedly your genes are influential. Nobody can predict the speed of bodily decay individually; all we can say for sure is that it will happen. The tide is going out. You can’t stop it.

I happen to be a very healthy person, and I run every day to stay fit. I don’t feel like an old man. However, I run the same 4-mile route repeatedly, and I time myself. Year by year I get slower. Some years back I was kvetching about this to my doctor, who is also a runner. “Why don’t you turn off your watch?” he asked me.

So, no sympathy from him. I saw his point but I’m not quite ready to turn off my watch. I want to see how fast I go, even if it’s a picture of predictable deterioration. My son, who ran the route in high school, asked me my time. He was appalled when I told him. “Dad,” he asked, “can’t you try harder?”

As a backpacker I used to carry a heavy pack at high altitudes for ten miles a day. Now I am finished at about six or seven miles. I used to cross streams on logs without slowing down; now I’m a tipsy danger to myself. I’m objectively aging. My body is gradually losing its capacity.

What’s weird is that I don’t feel any different. I observe the changes, but they seem to be taking place without my involvement. It’s like I am watching somebody else’s loss.

I notice this with older people who fall—say, at night, on their way to the bathroom. Oftentimes they fall multiple times before they are willing to use a walker to get around. “That can’t be me falling down,” they seem to say. “That was just a one-time, incomprehensible and unpredictable accident.”

Somehow, though, we know. We show our awareness by how cautious we become. I’m very careful when I’m going down stairs or descending a steep slope. My caution began ten years ago after I fell off my bike and hurt myself badly. I’m not conscious of worrying about such a fall, but I realize I hardly ever ride my bike anymore. In my younger years, I never thought about falling. I did fall, of course, especially as a child, all the time. The knees of my trousers were constantly being repaired. However, it meant very little to me. I picked myself up and went on. That’s very different now. I am aware of my vulnerability.

My aging body continues to surprise me. I hardly can believe that it’s me who has grown so old. And this loss is the foundation of many other losses.