It was 2006. Winter, and I was picking up my oldest son, Sam, at preschool. My friend Laura and I were going to take our boys and our bundled up baby girls ice skating. The gear was packed, and the plans were made, and Sam was running wildly around the cloakroom, disregarding again and again and again my pleas that he put on his coat and his boots. I asked him. I asked him again. And again. And then—

“Sam, if you don’t put your boots on right now, we’re not going ice skating.” Sam blew past me, giggling infuriatingly, with no sign of slowing down. I was taking a deep breath to ask again when his preschool teacher, Karen, tapped me gently on the shoulder.

“You know you can’t go ice skating now, right?”

I looked at Sam, who was nowhere near his boots and coat. I looked at Laura, who shrugged. Sam laughed. I seem to recall squaring my shoulders.

“You’re right,” I said. “We’re not going.”

I have no idea if Karen (who really wasn’t a busybody at all) meant for her words to have such an impact, or if she really even meant them at all. But what she said both struck me, and stuck with me. If I expected my words to have any impact on Sam, I needed to say only what I meant, and I needed to mean what I said—every time.

Sam didn’t believe we wouldn’t go ice skating until we were pulling into the garage, and then he cried for an hour. It was a miserable afternoon. But it truly did pay off, so much so that I remember it all these years later. The next time I told Sam to put on his boots, he put his boots on. And I felt different. I was a relatively new parent, living in a new place, barely freelancing, and struggling to figure out who I was in these new roles. To be honest, Sam was running roughshod over me. One afternoon’s refusal to put his boots on was not the whole of it, by any means. Sam and went through something along those lines daily, if not more often.

Karen’s words reminded me that as much as I was trying to figure out who I was as a parent, one thing needed to be clear: I needed to be the parent. If I made a promise, I needed to keep it. If I spelled out a consequence, it needed to happen.

At some point, I told my husband the story. We made a promise to each other that we’ve largely kept: no broken promises, no idle threats. If we tell a child that if she doesn’t sit down, she leaves the restaurant, then that’s exactly what happens. If we say “one more word out of you, and you’re not going to the birthday party tomorrow,” then after that one word, we have a phone call to make.

We’ve made some mistakes. Sometimes a punishment is larger than the crime, or bigger than we really intended. Once in a while, we have to eat our words—who were we kidding, even though you hit your sister again, you’re still coming on the plane to Grandma’s house. And (probably too often) we sometimes wimp out and give in to the plea for “one more chance” to get it right.

But mostly, our system feels successful—not necessarily for our children, but for us. Ask me in 30 years, and I’ll tell you if this (along with all the rest of our muddled-up parenting strategies) “worked.” What I know it does is to force us to watch our own words as parents. We’ve developed a shorthand code to consult one another before promising a child that continued misbehavior means we’ll leave the party or skip the afternoon’s plans. We think before we say “no.”

Would it really have mattered, in the grand scheme of things, if I’d given Sam “one more chance” to put those boots on? If we’d gone skating that day? Of course not. In fact, reading this, I admit it—I feel retroactively sorry for that long-gone excited little boy. It wasn’t the one moment that mattered, but the direction it pushed me in. Karen’s words were just what I, uncertain and finding my way, needed to hear. That one afternoon’s missed ice skating on the pond made me a better parent.

What’s the best single piece of parenting advice anyone ever gave you, and why?

A shorter version of this post appeared in print on Oct. 11, on Page D2 with the headline “Say What You Mean, and Mean It.”