My toddler threw an epic tantrum in public. The advice I got from another mom stuck with me for years.

• My daughter skipped the terrible twos, and I thought I was safe from tantrums.
• Then, when she was 3, at a fair, she threw her shoe at another kid because she was angry at me.
• Another mom saw my frustration and gave me parenting advice that has stuck with me for years.

"She's perfect," my pediatrician said the day she met my daughter.

And she was. She was an easygoing baby who'd leapfrogged the dreaded terrible twos. I thought we were past tantrums and meltdowns.

Our lives followed a predictable rhythm: five incredibly structured school days followed by two stay-at-home days. I lived for precious time dedicated to my own children, a reprieve from my working mother's guilt.

Then she threw an epic tantrum at a fair.

She didn't want to leave

One Saturday, I'd planned to meet a friend at the town harvest fair. My 3-year-old walked to the closet and homed in on a newly acquired hand-me-down black velour jumper.

"I want to wear this, Mommy."

It was September in New England, so I knew that if she wore the jumper, she'd be sweltering by late morning. I pulled leggings and a tee from her dresser and offered them up as an alternative, explaining that she might not be comfortable with the outfit she chose.

I worried I wouldn't be comfortable, either. As a teacher in town, I knew we'd encounter parents and kids. I worried how my toddler's self-styled get-up would reflect on both of us.

But she was determined, so I relented.

As anticipated, it was turning out to be a very warm day. My infant, who'd been peacefully snoozing in her stroller while her big sister and I made our way through the fair, starting at the school bake sale and ending at the bounce house, had woken. It was time for us to leave.

I reached my hand out for my pink-cheeked toddler to grab hold of and cheerfully said, "Time to go."

"No," she said, then dropped to the ground, smack dab in the center of the town green.

I stood with one hand on the stroller, stunned. Was what I thought was about to happen actually happening?

Was my easygoing, perennially peaceful child actually on the verge of her first tantrum? Here? In public?

She started shouting

I wiggled the fingers on my outstretched hand and gestured for her to come and take my hand. "Let's go," I said in an artificially sweet voice.

"I. Want. To. Stay!" she shouted.

I froze, disbelieving that my perfect daughter was actually going to have a full-scale tantrum. In public. I heard the crackle of the Velcro strap, followed by the vision of a size nine patent leather Mary Jane flying through the air, falling to the ground after making contact with a little girl.

I watched the stunned child look up at her dad and then turn in our direction.

Making eye contact with the little girl, my heart sank. The big, brown eyes belonged to a sweet, shy little girl, who, as luck would have it, was a student of mine.

Rushing to her and her dad, I blurted, "Iamsosorry."

The girl's dad said nothing and handed me the shoe.

Mortified, I strode to my daughter, scooped her up, and placed her on my hip.

I reached for the stroller with the other. Out of nowhere, a mom from the previous year's class appeared beside me.

I was horrified

"Hey," she said, placing her hand on mine. "You OK?" I told her I was horrified at my daughter's actions. She didn't judge me, and instead, warmly and with a smile, said, "We've all been there."

I didn't believe her. I couldn't picture this chill mom and her chill kids falling apart in public. But she doubled down, "Every single one of us."

Those words of unity were the words I needed to hear. They were words of compassion instead of judgment, an acknowledgment that I was doing my best and that my kids were, too.

Decades later, I find myself repeating her compassionate words in my head when I encounter another stressed-out mom doing her best to manage her little one's big feelings and aloud when it feels like a mom really needs to hear the healing words to let her know she's not alone.

We've all been there. Every single one of us.