On the night of his last Late Night Show, I saw something in David Letterman’s eyes I hadn’t seen before.

Come to think of it, his smile was broader than usual, too.

Letterman was saying goodbye to late night television as his mentor Johnny Carson did before him. But unlike Carson, Letterman was pulling himself out of the game at a time of his own choosing. He looked relaxed, happy, grateful, and a little like he was looking forward to the future.

I loved his trip down memory lane; his stint at the Taco Bell drive-thru, his conversations with kids through the years, even the “Stupid Pet Tricks.”

But the moment I enjoyed most was the look of true happiness and pride on his face as he introduced his family from the audience. He even introduced young son Harry’s best friend to the nation. I can almost hear him telling Harry, “Of course I’ll introduce your friend, too! Hey, it’s my show, and I’m your dad!”

I think David Letterman enjoys being a dad. That may be the biggest reason he’s saying goodbye to TV. He’s already missed so much time watching Harry grow up.

We’ve watched Dave grow up, too. When he began on late night TV 33 years ago, he was young and brash, the class clown who had his own show and would brandish that trademark Letterman smirk for a full hour each night.

But as the years passed and the bushy hair thinned and grayed, Dave began to show a softer side. He had quietly become a family man. We began to read more about his family vacations and less about his tussles with network executives and sponsors.

As I watched Letterman, I thought about my own journey in life.

I was also a class clown. OK, I still am. In fact, I’m a card-carrying member of the Wise Guys of America club. But fatherhood changed me in ways I could never imagine.

I feared I would be a horrendous father. I was terrified at the prospect of holding a young life in my arms and knowing there would be a child in this world who would depend on me for — well, everything.

But something happened almost immediately. I fell in love.

The child in my arms was something I helped to create. She was part of me. I would have a front row seat for every facet of her life. And that rocked my world.

As a bonus, I was able to relive my own childhood through her. I got to play silly games with her, watched her ride a bike for the first time, and took her to those father-daughter dances where we did the Macarena and drank over-sweetened punch.

And I made plenty of mistakes along the way.

Thinking back, it was probably a bad idea to let her watch Stephen King’s movie “It” with me when she was seven. My twisted mind told me at the time that since she loves being frightened, she would probably like it. I called that one wrong.

We bonded in a special way as most dads and daughters do.

I found an old photo recently of the two of us crossing a downtown street. We were on our way to a preschool gathering, and I was holding her hand.

It’s one of my favorite pictures. You can’t see either of our faces. It’s just the two of us walking away from the camera holding hands. We must’ve done that hundreds of times, but that simple photo represents a time when she really needed me.

And to be honest, I needed her, too. I still do.

So I’m glad David Letterman, at the age of 68, will get to step away from TV for a while and enjoy the part of life that I know he will remember most one day.

Being a dad and watching Harry grow up.