'Shark Tank' investor Robert Herjavec shares the best advice Mark Cuban gave him

Mark Cuban
John Lamparski | Getty Images

Robert Herjavec and Mark Cuban, both judges on ABC's "Shark Tank," haven't always seen eye-to-eye.

Herjavec, the multi-millionaire owner of cybersecurity company Herjavec Group, and Cuban, a billionaire entrepreneur and owner of the Dallas Mavericks, often argue over investing deals. In fact, Herjavec once admitted that he hated Cuban for the first two years he was on the show.

But just recently, the two had a conversation over lunch in which Cuban offered Herjavec a piece of valuable career advice.

"[Cuban] looks and me says 'You know? You're a good guy. And so I'm going to give you a piece of advice. You have to dream bigger,'" Herjavec recalls.

"You're always trying to protect your downside, think about the upside."

It was a rare moment where the two agreed on something.

Mark Cuban and Robert Herjavec attend a "Shark Tank" breakfast on September 23, 2016.
Todd Wawrychuk/ABC via Getty Images

The fear of risk or downside can hold many talented entrepreneurs and professionals back, according to the multi-millionaire.

Focusing more on the upside, or your potential for success, pays off, Herjavec tells CNBC in a video-call from Google's Headquarters, where he was advising young entrepreneurs for the "Dreamvention" contest with Frito-Lay.

He cites the time it took him to expand his cybersecurity company as an example. Before Herjavec's start on "Shark Tank," the Herjavec Group operated only within Canada.

"I never thought about expanding outside of Canada," he tells CNBC. "I don't know why, maybe I didn't have the confidence, maybe I didn't believe I could."

But three years ago, he finally made the leap. Today, the company operates in the U.S., Canada and the United Kingdom.

In their recent conversation, Cuban reminded Herjavec to keep thinking about new opportunities, instead of worrying about the risks.

Think about the upside.
Mark Cuban
self-made billionaire and entrepreneur

As to whether or not the two men still dislike each other, Herjavec confirms they're on good terms.

Though they still "battle" constantly, "We like each other," he says.

Mark Cuban: If I lost everything and had to start over, here's what I would do
Mark Cuban: If I lost everything and had to start over, here's what I would do