At twenty-three, my purpose was to become someone. At thirty-five, my purpose was to build something. At forty-seven, my purpose is to leave something behind.

These are not the same purpose. They are not even the same person.

I did not understand this when I was young. I thought purpose was a fixed star you discovered once and followed forever. Find your passion, they said. Find what you love and do it until you die. I believed this. I searched for the one thing that would define me permanently.

Now I know: there is no one thing. There are many things, arriving in sequence, each one right for its time and wrong for the time that follows.

When I was in my twenties, I wanted experience. I wanted to taste everything, try everything, become everything. I changed jobs constantly. I traveled without plans. I started projects and abandoned them when something more interesting appeared. My parents worried I was directionless. My relatives whispered that I would never settle down.

But I was not directionless. I was exploring. My brain, I understand now, was built for exactly this. The twenties brain craves novelty. It rewards risk with pleasure. It needs to experiment because it is still deciding who to be.

Every abandoned project taught me something. Every wrong turn showed me a path I did not want to take. By thirty, I had accumulated enough failures to know what success might look like. The chaos had a purpose. I just could not see it while I was inside it.

Then something shifted. Around thirty-two, the hunger for novelty faded. I no longer wanted to try everything. I wanted to build something. One thing. Something that would last.

I got married. I committed to a career. I bought an apartment and stayed in it. The same person who could not sit still for a year now found comfort in routine. The same person who feared commitment now craved it.

My younger self would not have recognized me. He would have called me boring, sellout, domesticated. But I was not betraying him. I was becoming someone else. Someone whose brain had restructured, whose hormones had shifted, whose needs had evolved.

The thirties are for building. For laying foundations. For investing in things that take decades to mature—careers, marriages, children. The brain that once screamed “what’s next?” now whispers “what lasts?” This is not decline. This is development.

My friend Karim resisted this transition. He stayed in his twenties purpose well into his thirties. He kept chasing novelty, kept avoiding commitment, kept living like the future would never ask for an accounting. At thirty-eight, he looked around and found he had built nothing. No deep relationships. No accumulated expertise. No foundation to stand on.

He was not lazy. He was fighting his own development. He was trying to remain someone he no longer was.

I am forty-seven now. Another shift has begun. The building phase is ending. The leaving phase is beginning.

I think about legacy now. Not in grand terms—I will not build monuments or write books that change the world. But in small terms. What will I pass on? What have I learned that someone younger needs to know? How can the struggles I survived become shortcuts for those coming behind me?

I find myself wanting to teach. To mentor. To share. This is new. In my twenties, I had nothing to share. In my thirties, I was too busy acquiring to think about giving. Now the giving feels urgent. The clock is visible in a way it was not before.

This is what the forties bring: mortality. Not as abstract concept, but as felt reality. I have fewer years ahead than behind. The question changes from “what will I become?” to “what will remain?”

Some people call this midlife crisis. But it is not crisis. It is development. The brain at forty is not the brain at twenty. New networks have activated. Wisdom has accumulated. Priorities have naturally, inevitably shifted.

The crisis comes only when we fight the shift. When we try to maintain twenty-year-old purposes in forty-year-old bodies. When we refuse to let the mission evolve.

I know men my age who are still chasing the twenties dream—novelty, adventure, the next exciting thing. They leave marriages, quit stable jobs, buy motorcycles. They think they are reclaiming youth. But youth cannot be reclaimed. They are running from a transition that will catch them eventually.

I also know men who built empires in their thirties and cannot stop building. They have more money than they need, more success than they can use, but they keep accumulating. They have not heard the forties whisper: enough building. Time to give.

Each decade asks a different question.

The twenties ask: who are you? The thirties ask: what will you build? The forties ask: what will you leave?

Answer the wrong question for your decade, and life feels off. You are working hard at something that no longer matters. You are solving yesterday’s problem.

I do not know what the fifties will ask. I suspect it will be something about acceptance. About peace with what is, rather than striving for what might be. About letting go of purposes that have been completed.

And the sixties, seventies, eighties—each will bring questions I cannot yet imagine. New missions for new versions of myself that do not exist yet.

This is the truth no one told me when I was young: you are not one person with one purpose. You are many people, arriving in sequence, each with their own mission. The child becomes the adolescent becomes the young adult becomes the middle-aged becomes the old. Each transition is a small death and a small birth. Each new self inherits the memories of the old but does not share its needs.

Purpose is not a noun. It is a verb. You do not have purpose. You purpose. Continuously. Differently. According to the decade you inhabit.

The twenty-three-year-old who searched for experience was right for his time. The thirty-five-year-old who built a family was right for his time. The forty-seven-year-old who wants to teach is right for this time. None of them was the final version. None of them had the permanent answer. They were all just travelers, doing the work their decade required.

I will become someone else again. Several someone elses, if I am lucky enough to live long. Each one will look back at me and wonder how I could have cared so much about things that no longer matter. Each one will be right to wonder. Each one will have their own concerns, their own purposes, their own missions that will seem permanent and prove temporary.

This is not sad. This is life. The river does not mourn the water that has passed. It simply keeps flowing.

I am flowing.

We are all flowing.

The mission changes because we change.

And that is exactly as it should be.