Successful business owners have to be decisive and confident. But they also need to learn to step back and shut up from time to time.

Just because someone has built a successful business doesn't mean they have all of the answers, and any entrepreneur needs to be receptive to outside ideas, and even criticism, according to self-made millionaire Marcus Lemonis.

Lemonis is the CEO of Camping World, a company that sells RVs and has a market value of roughly $1.7 billion. He's also the star of CNBC's "The Profit," which sees Lemonis regularly try to help small business owners improve their fortunes. In the most recent episode of "The Profit," Lemonis meets a husband and wife who run a small chain of bagel shops in Chicago, called NYC Bagel Deli, who exemplify his point.

Corey and Laurie Kaplan have owned the Chicago bagel chain for nearly two decades — its profitable, but the Kaplans want to expand. Corey just happens to be getting in his own way.

"[Corey] Kaplan has a long history in the industry… and an ego to match" Lemonis says during the episode.

Corey Kaplan wants to open 10 more locations, but Lemonis thinks the Kaplans aren't getting the most out of their current business; he believes their biggest store alone could generate an additional $1 million in annual sales with a few tweaks. The business has "gone stale" and isn't growing as quickly as it should, and part of the reason for that is the branding is "uninspired" and generic, Lemonis tells the Kaplans.

That's where Lemonis' relationship with the Kaplans hits a snag.

Corey, who started out working at his father's bagel shop in New Jersey over three decades ago, boasts that "they didn't even know how to say 'bagel' in Chicago until I got there," on the show.

"I'm not prepared to say, 'Some new guy came in and now we're different,'" Corey, who has an established customer base, tells Lemonis.

Corey has a big personality and he likes being in charge, but he also tends to talk over his wife and dismiss any of her business ideas, as well as those from Lemonis.

Later, when Lemonis asks why the Kaplans don't put any leftover bagels to use by making and selling toasted bagel chips, Corey is once again dismissive even though Laurie says she's wanted to pursue that idea for years.

Corey's inability to accept advice — even from his wife, is keeping his business from reaching its potential, according to Lemonis.

Whenever Corey's business runs into a problem — whether it be stagnant sales or wasting leftover bagels — "he's used to normally just stepping in front of everybody and just solving it" himself, Lemonis says. But that approach obviously wasn't working.

"In order for this business to grow," says Lemonis, Cory is "going to have to be quiet" and listen.

In other words, if you want to be a successful entrepreneur, you have to be willing to listen to other people's ideas instead of trying to fix everything yourself.

CNBC's "The Profit" airs Tuesdays at 10 p.m. ET .

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