Julia Stewart has enjoyed a long, successful business career. Her parents, both high school teachers, are a huge reason why, she says.

Stewart, 68, became IHOP's first-ever female CEO in 2002. Five years later, she led a risky takeover of Applebee's that combined the two brands into one company, called Dine Brands. That organization now has more than 3,500 total locations and a market value above $600 million.

She resigned as CEO of Dine Brands in 2017. Instead of retiring, she launched a wellness company called Alurx three years later — because building a startup was a challenge she hadn't yet encountered, she says.

"I grew up an only child with two school teachers [who were] constantly, pretty much, engraving in me: 'You should be learning for the rest of your life. You should never stop working. You should never stop reading," Stewart tells CNBC Make It. "That became, sort of, a mantra for me and my leadership style."

Stewart embraced the lesson early while growing up in San Diego, she says — taking that attitude into a teenage waitressing job, ironically at an IHOP.

Her goal was to save enough money for a car. But her favorite part of the job was actually collecting tips at the end of a shift, because her manager would share observations on how she'd done and where she could improve to offer better service and earn more money, she says.

"I loved getting feedback every day," says Stewart, adding: "There was always this notion of wanting to make it better. And I think that just stuck with me."

'I don't have to be the smartest person in the room'

Stewart spent the 1980s working as a marketing manager for restaurant brands like Carl's Jr. and Burger King. After rising to a vice president role, Stewart decided she'd never become a CEO without experience in a role that directly steered business decisions.

She left her "cushy marketing" role to join an executive training program at Taco Bell that required her to put on a uniform and spend a few months working on the restaurant floor as an assistant general manager.

Stewart embraced her parents' lesson, she says: The more she learned about how Taco Bell locations made money, the more she could apply those lessons on a large scale. Good leaders need to recognize they might not always have the answers, and be secure enough to seek help from anyone, she adds — including junior staffers at a fast food joint.

"I think as you get older and you become successful, you realize: 'I don't have to be the smartest person in the room,'" she says. "I've never had somebody say, 'No, I'm not going to help.'"

Seeking out new challenges

Constant learning is a common trait among successful leaders.

Jeff Bezos, for example, crafted a list of leadership principles for Amazon's employees during his time as CEO. They included the idea that good leaders should always "seek diverse perspectives and work to disconfirm their beliefs."

Bezos' ability to remain "open and curious," even after Amazon's massive success, left an impression on his successor in the CEO role, Andy Jassy.

"Great leaders keep listening to additional inputs — people inside of the company and outside the company — and keep adjusting their opinions and their ideas as they learn more," Jassy told Fortune in January, adding: "You shouldn't have one opinion, and stick with that forever."

In Stewart's case, she spent the three years between leaving Dine Brands and founding Alurx researching her options, she says. Once she settled on doing something health-related, she interviewed doctors, psychologists and other medical staff to better understand the industry.

The same habit is proving useful again now, as she navigates the scrappier world of entrepreneurship for the first time, she adds.

"I wanted to do something that was different, that would challenge me in a different way," says Stewart. "And that's exactly what's happened."

Want to be a successful, confident communicator? Take CNBC's new online course Become an Effective Communicator: Master Public Speaking. We'll teach you how to speak clearly and confidently, calm your nerves, what to say and not say, and body language techniques to make a great first impression. Sign up today and use code EARLYBIRD for an introductory discount of 30% off through July 10, 2024.

Plus, sign up for CNBC Make It's newsletter to get tips and tricks for success at work, with money and in life.