Entrepreneurs

The No. 1 lesson 'Shark Tank' star Kevin O'Leary learned after being fired from his first job

Today, Kevin O'Leary presides over a multitude of companies bearing his last name: wine business O'Leary Fine Wines, financial company O'Shares Investments and private equity firm O'Leary Ventures.

He's also famous as a judge on ABC's "Shark Tank," through which he's invested in businesses like Plated — a meal delivery company that sold to Albertson's for $300 million. O'Leary says it was the largest exit in the history of the show.

If you ask him where his inspiration to be an entrepreneur comes from, the answer is an unlikely experience: being fired from a mall ice cream shop as a teenager.

"I was very excited about it, it was my first job," O'Leary tells CNBC Make It of landing the gig as an ice cream scooper. "The girl I was interested in worked at the shoe store right across the mall."

The place was called Magoo's Ice Cream Parlour, and O'Leary was hoping he could use the job's proximity to his crush to catch some time with her during their lunch hour.

At first, things were going pretty well. Then his boss asked him to scrape some gum off the floor of the shop.

"What happens when you're sampling ice cream — you're chewing gum, you take it out, you throw it on the floor," where it sticks, O'Leary explains. It was a particularly irksome task to clean up gum in this store, which he says had Mexican floor tiles. But the owner deemed it a job for him to tackle.

He recalls her saying, "Thank you for your work today. Before you leave, get down on your knees and scrape all the gum off the tile so it's clean for tomorrow."

O'Leary looked past his boss and he "could see the girl I liked right across the mall," he says. "I saw her looking at me, and I thought if she sees me on my knees scraping gum, I'm screwed."

So he took a stand. "I was hired as a scooper not a scraper," O'Leary remembers telling the boss.

She fired him on the spot.

"Yikes," he says. "I went home, and explained what happened to my mother. She said, 'That was a bad mistake.'"

Then his mom relayed advice he would never forget. "There's two types of people in the world: those that own the store and those that scrape the s--- off the floor, and you have to decide which one you are.'"

It's inspired his success ever since.

Kevin O'Leary
Scott Mlyn | CNBC
Kevin O'Leary

"I made up my mind that day, I want to be the owner, not the scraper. And I've never worked for anybody ever since," he says. "That was my motivating moment.

"I wish I could find that [boss], she changed my life forever."

For him, getting fired by the owner of Magoo's Ice Cream Parlour worked out alright. "I can afford to go find that mall and bulldoze it today because of her," he says. "Thank you very much."

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Disclaimer: CNBC owns the exclusive off-network cable rights to "Shark Tank."