I was at my optometrist’s office today when my youngest son decided to revolt.

There I was, squeezing my face into various plastic implements, deciding which view of the distant tree was clearer, getting my eyes blasted by very bright lights and puffs of air, and he decided to have some fun. What do you do when you are 5 years old and you want to have some fun in a place that is not meant for children? You mess with the lights. You touch buttons. You interrupt the doctor when he is talking to his patient, your mother.

“Stop!” I pleaded with him as he touched the glass model of a real eye.

“You know better than this!” I said as he turned off the lights in the middle of my conversation with the optometrist.

“This is naughty!” I said as he reached for the button that raised and lowered the exam chair.

“You know, I went to a kindergarten graduation today,” my doctor said, as my kid flipped the lights back on. “I’ve wanted my son to grow up and stop doing the little things kids do, but today, I wanted to hold on to those moments a little longer. Before you know it, it will be over, and they will be gone.”

I knew what he was talking about.

My 5-year-old has so much joy. He told every person he saw this week that it was his birthday. He makes friends with strangers. He has a wonderful imagination, a witty sense of humor and a raw current of excitement that energizes everyone around him. Those are the blessings of his age.

On the flip side, the boy is stubborn. He is so strong-willed. And when he disobeys, it is not personal or devious, but when his wants are in conflict with a directive from an authority figure, there is no talking him down. It is as though he cannot hear the words coming out of my mouth.

He smiled as he sat down in the chair in the exam room, after he scooted it around the office trying to determine if it swiveled. He smiled still when he hopped up 60 seconds later, even though I asked him to try to stay in the chair for the rest of the visit. He was a picture of cheerfulness as he bounced up to the front desk and took three fun-sized candy bars and asked me to open them minutes after he had so completely ignored me. None of it was meant to be hurtful — he’s driven by a strong sense of doing what his heart tells him to do.

OK, maybe he is a little spoiled. Maybe he gets his way a lot of the time. But he is my youngest child. My buddy. My guy who wears blue glasses and asks me to cuddle every night. In the fall, he will be going into kindergarten to face the pains and pleasures of growing up. I hate to see the pain. I hate to think of him caring more about what his peers think than what that robust little beating heart in him says.

In a short amount of time, I won’t be with him all day to tell him how great he is and how much I love him. I know that, and I am trying to hold on to these moments.

But soon after my doctor reminded me of the fleeting beat of childhood, my son upped the ante of interference and my stress level went through the roof. To be fair, this particular day was busy. In the morning, we helped my daughter’s class at her school’s field day, and my youngest son dutifully traipsed around a field for two hours, never straying too far or getting in the way. We ran errands to get ready for a camping trip, then we came home for lunch and to get a few things done. When we left for the eye doctor, I knew time was tight. I needed the doctor to be on time and fast so I could pick up my other son from school and get to a work assignment.

As usual, I had more to get done than I had time to do, but I blamed my 5-year-old for making me late to pick up my other son. Sure, this pre-kindergartener should have listened to me, but as soon as I saw him hand his big brother one of the fun-sized candy bars he poached from the doctor, my heart melted.

Time is short. And sometimes it takes an eye exam to see just how important it is to hold on to every moment.