I first became aware of the relentless process of aging in an unexpected way. I was a college pastor, 37 years old, and a student from the campus across the street had come for an appointment. She talked out her problem, and we prayed. As she got up to leave, she said with a warm smile, "Thanks very much for seeing me; I thought it would be good for me to talk to someone middle-aged."

Me, middle-aged? It was a brand-new and unexpected thought. I pondered it for some time after she left. I'm not middle-aged, I thought. I am young, not that much different from the hundreds of students I preach to every Sunday.

But the truth slowly sank in, and, since then, people here and there have managed to remind me of my aging process. For example, I was holding a church conference in Western Canada when I was in my early 60s. As I crossed the conference grounds from the lodge to the meeting place, singing to myself, I saw my friend Maurice coming toward me. He stopped, put his hand on my forearm, and said in a solicitous voice, "At your age, you shouldn't be walking and singing at the same time."

Later that year, my wife, Kathleen, and I were driving across Michigan on Interstate 94. It was late afternoon and time to quit for the day, so I pulled into a motel. Inside, I asked the usual questions: "Do you have a non-smoking room for two? Preferably on the main floor?" The man at the desk studied his charts and then, smiling as if he was going to be helpful, said, "I can give you a handicapped room. Fully equipped." It was another jarring moment. Did I look that decrepit? I wondered.

But the coup de grâce came a few months ago, administered by the boss of a roofing crew replacing shingles on a house next door. I asked him to look at my ...