Judging from a variety of survey data from multiple cultures, people tend to be happy in their 20s and early 30s before hitting a less-happy trough in their late 30s and 40s, then returning to happiness in their early 50s. The line graph for this looks like a “U” stretched out on both sides, or, if you prefer, like a smile.

The predominant explanation seems to be that when we are young, we are ambitious and optimistic.

We feel good physically and have our lives in front of us. By our 40s, we start to worry about things we have not done yet, stymied by the realization “this” might be all there is. But by our early 50s we move on toward thinking “this” is not so bad after all.

At 54, I’ll admit my own experience seems to fit the pattern. I have less energy, my career has likely plateaued, and my parents will probably soon need closer care, but I still feel more satisfied. Is this because I got enough of what I desired? Or is it, perhaps, because I stopped desiring so much, or at least started desiring different things?

I teach comparative religion, so I know who spoke most clearly about satisfaction and desire. The Buddha taught these Four Noble Truths:

• Life is dissatisfying.
• Dissatisfaction is caused by desire.
• Dissatisfaction will end only when the desires are extinguished.
• The way to extinguish desires is to follow spiritual discipline. (For the Buddha, spiritual discipline meant the Eightfold Path).

I’m not kidding anybody: I have not extinguished all my desires. And I do not have much spiritual discipline. But maybe life is adjusting my desires whether I asked for it or not.

What really changes as we hit 50? Perhaps most importantly, our time horizon changes. I’m not sure when my career will end, but I know I can see it from here. This means my goals change. I want to do something significant, but I’m realistic, circumspect, about what that might be. I cannot pretend the possibilities are infinite; the constraints are obvious, with “time” at the top of the list.

A Buddhist statue on display at the Nelson-Atkins Museum of Art in Kansas City, Mo. Religion News Service photo by Sally Morrow

My definition of “significance” has changed too. I have a clearer sense of what matters to me, of whose opinions matter to me.

Finite time constraints and a clearer sense of values combine to offer the greatest gift of all: an improved ability to live in the present. At a certain age, you realize that clinging to past mistakes is futile. Even better, you stop yearning for some ideal future because experience teaches us the ideal is probably not forthcoming.

When I am with my grown children now, I think of that time as perfect by itself, not as a means of getting to something else. God willing, some future time with my grandkids will be even more perfect. (I realize “more perfect” is redundant, but I’m told it still applies to grandkids.)

Mindfulness — living in the present — is part of the discipline the Buddha taught in the Eightfold Path: right view, right intention, right speech, right action, right livelihood, right effort, right mindfulness and right concentration. As a younger man I didn’t want to hear it because I had places to go. I yearned for something else.

I have not become a Buddhist. I am too attached to several of my desires, unwilling to let them go. But I see the structure of life bending me toward this wisdom and applying some form of this discipline to me whether I like it or not. Considerable evidence suggests similar changes happen across cultures; the U-curve applies in a variety of settings.

I’m clear-headed about the benefits of living in a society where people do yearn and strive, where cars get safer, food gets cheaper and information gets more widely available. People who eschew “grasping” still reap the benefits of other people’s materialistic ambitions.

Arthur E. Farnsley II is professor of religious studies at Indiana University-Purdue University Indianapolis and author of “Flea Market Jesus.

I’m also clear-headed enough to know that I am privileged, that a 54-year old me who has plenty is in no position to tell younger people to stop letting their desires rule them.

I can’t even make this a sermon about how I wish I’d learned all this earlier because, honestly, I knew about spiritual discipline and consciously rejected it. Let’s face it: Grasping is bound up with energy and energy is a source of joy, even if dissatisfaction is inevitable.

But if I cannot preach mindfulness and extinguishing desires to anyone, I can still recognize the relationship between satisfaction and desires when I see it. As I learned about the U-curve, I realized that those of us who live long enough and enjoy good health see our lives bent back toward the place where, maybe, we should have started long ago.

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