A few days ago, my wife and I drove our daughters to their first day of school. I hardly noticed that my breathing was becoming shallower as we got closer. I didn’t want to notice it.

“You know,” I said, “I’m not going to cry when we say goodbye to the girls today, but I understand why parents do.”

At the front of the school, a teacher instructed us to take our four-year-old to one building and our five-year-old to another. I said a quick goodbye – too quick – to my five-year-old, and took my other daughter’s hand. I tried not to notice the slight lump in my throat.

When my daughter and I got to the four-year-old class, my daughter took a seat by herself, and I gave the teacher her pillow and blanket for nap time.

“Don’t go, Daddy,” my daughter said with fear in her eyes.

I looked over at a professionally dressed, middle-aged woman who was saying goodbye to her child with ease and thought, Just do what she’s doing. And then I did it — I said goodbye, turned around, walked away from my daughter, and then made a fatal mistake: when I got outside, I looked into the window of my daughter’s classroom and saw her sitting by herself with her head down.

The moment broke my heart, but I didn’t want to forget it so I snapped a picture and walked away (see photo). That’s when the first tear broke through, but I thought, Be calm, this isn’t the place for a breakdown. Then I readied myself to go to the other building and say goodbye to my five-year-old. But when I got there it was too late. She was already in her class.

“I can’t do this,” I said to my wife, who was in the lobby. And then I looked down, darted towards the door, and bumped into the hordes of parents and kids streaming into the building. Hot tears gathered in my eyes, and just as I made it out of the building, they started streaming down my face. The only thing I could do at that point was walk to my car and tell God how bad it hurt.

I know a lot of parents can relate, and it’s not only the ones who just dropped their kids off for their first day of school. Whether you’re sending your kid to kindergarten, college, or watching them get married, these moments are hard because they’re such an unsettling confrontation with reality. It’s the reality that the time with our kids is limited, that other people might influence them in ways we never wanted, that we can’t protect them from the unpredictabilities of life.

That reality was shaking the tears out of me as I walked away from the school that morning. I was dealing with the fact that, as my pastor says, “They’re not our kids – they’re God’s kids. He just drops them off with us for a little while, and then we return them to him.”

My pastor is right, no doubt about it. And as my girls venture out into the world, I’m sure God will be a better Father to them than I could ever be. I just didn’t realize until the other morning how hard it would be to begin the process of giving them back.

This article originally appeared on Fox News Opinion at FOXNews.com.  If you’d like an email with a weekly recap of what I’ve written, click here.  You can also keep up with my latest articles (and more) on Facebook or Twitter.