For those looking to get ahead, the best career training might not come from a classroom or a corporate internship, but from a low-wage job in the service industry, says Jeetu Patel, now president and chief product officer at Cisco.

Before overseeing products at the tech giant, which has a market cap of about $270 billion, he spent his early 20s waiting tables at Sizzler, a steak house chain, making just $4 an hour. Far from something to hide, he says the experience shaped his work ethic and people skills—and ultimately helped him climb Silicon Valley’s corporate ladder.

“I think everyone in the early part of their career should work in the service industry somewhere,” Patel tells Fortune. “I think it’s so great to really get, you know, like, a level of appreciation for hospitality and customer service, and it just wires you differently.”

As a young man, he was introverted and even had a stutter. While there were easier ways to make money, he deliberately chose a customer-facing job to push himself out of his comfort zone.

“What happened while waiting on tables is—and it wasn’t even a conscious thing—that I was an introvert, and I realized if I don’t talk to people and don’t entertain them and give them a good experience, I’m not going to make a tip,” Patel says. “And if I don’t make a tip, then I’m just working a lot of long hours without the return.”

He would eventually go on to have leadership roles at tech firms like Doculabs, EMC, and Box before landing at Cisco. What ultimately helped him stand out, he says, was understanding that self-belief matters more than external validation—and that confidence, when grounded, can be a superpower.

“If you put your mind to something, you can basically figure out whatever you want to figure out.”

Patel’s message to Gen Z: Arrogance can be a killer

On the road to success, Patel thinks one of the biggest mistakes young professionals make is believing they can do it all on their own.

“Oftentimes, we let our pride and ego get in the way,” he says. “We’re like, ‘I’m going to try to be a self-made person.’ There’s no such thing as a self-made person; we live in an interconnected society where humans depend on humans, and so if you can stand on shoulders of giants, it just takes you farther.”

Because access to opportunity is not evenly distributed, Patel adds that receiving help isn’t something to feel guilty about. “If you have access to the resources and you don’t use them, then shame on you.”

Still, Patel warns Gen Z that confidence can quickly morph into arrogance. Instead, the key is to strike a balance between embracing opportunities that come your way while staying humble enough to recognize the privilege behind them and that others may have had to work much harder for the same chance.

The service-industry-to-C-suite pipeline

Patel is not alone in having risen from the service floor to the C-suite. Some of the world’s most prominent business leaders started out in customer-facing roles.

Amazon founder Jeff Bezos worked his first job at a McDonald’s outside of Miami, flipping burgers and cooking Egg McMuffins, an experience he’s said taught him responsibility, teamwork and how to handle pressure.

“You can learn responsibility in any job, if you take it seriously,” Bezos said in the 2012 book, Golden Opportunity: Remarkable Careers That Began at McDonald’s. “You learn a lot as a teenager working at McDonald’s. It’s different from what you learn in school. Don’t underestimate the value of that.”

Nvidia CEO Jensen Huang also began his career in the service industry—washing dishes at Denny’s. He often credited that job with instilling discipline and humility.

“No task is beneath me,” he said during a conversation with students at Stanford’s Graduate School of Business. “I used to be a dishwasher. I used to clean toilets. I cleaned a lot of toilets. I’ve cleaned more toilets than all of you combined. And some of them you just can’t unsee.”

But Gen Z may need to act fast to emulate their success as the kinds of jobs that have shaped many of today’s leaders may soon be harder to come by. A report released this week by U.S. Senator Bernie Sanders estimated that nearly 100 million jobs may be replaced by AI in the next decade—and fast food workers and customer service representatives are among the most vulnerable, with over 80% replacement rates.