“We’re going to be really demanding,” Khosrowshahi said recently on the Diary of a CEO podcast. “If you’re not performing, we’re going to let you know. And if you don’t fix it, we’re going to push you out.”

When Khosrowshahi stepped into Uber’s top role in 2017, he quickly implemented a new strategy to turn things around. At the time the company had been losing $2.5 billion to $3 billion a year, and was resting on some of its success, the tech leader explained. 

To get the business back on track, he took a hard look at his team and revamped the company’s work culture—including off-hours. 

“Part of working hard is sending emails to the team on a Saturday,” he continued. “And if I don’t get a response on Saturday, sending them an email on Sunday with a question mark. What’s going on?” 

So far, his leadership philosophy has been working: Khosrowshahi pointed out that last year, Uber generated $9.8 billion in free cash flow. And while he admits working at the ride-hailing company is no cakewalk, he says employees have real agency, learn a ton, and can make a tangible difference in the world. 

“While you will have worked hard, you’re going to have a great time,” the CEO said. “But don’t come here if you want to coast.” 

Fortune reached out to Uber for comment. 

Uber CEO says the most important skill in life is work ethic: ‘Life is about tradeoffs’

The Uber CEO’s demanding work culture isn’t just necessary for company transformation—he reveals it’s a core competency of success. 

“To me, the most important skill in life is a skill of working hard,” Khosrowshahi said on the podcast.

The two-time chief executive explained that professionals get too hung up on their career path, mulling over whether they should be a computer programmer or doctor, or study the liberal arts. But the real key to achievement isn’t picking the ideal line of work, Khosrowshahi says: Just work hard, and success will follow. 

He’s passing that same wisdom down to his kids, and advises others to follow suit; even as the top boss, he never lets up.

“I’m not going to let anyone outwork me,” the Uber CEO said. “They may be smarter, more talented, et cetera, but I’m not going to let anyone outwork me. And I think that’s a huge advantage that you have, and over a period of time, that advantage compounds.”

However, working hard doesn’t mean a never-ending grind 

Even Khosrowshahi sets boundaries around his personal time: Whenever he’s in town, he blocks off two hours to have dinner with his family. 

But just after the meal ends, he’s back to checking his emails at 9:30 p.m., and goes through his inbox again when he wakes up at 5:30 a.m. 

It’s possible to strike some balance while working hard, he insists—but something will always have to give.

“We believe in flexibility. People confuse lack of flexibility to working hard: You can work hard, and at the same time you can have flexibility,” Khosrowshahi explains. “Of course, there are tradeoffs. Life is about tradeoffs.”