Shark Tank's Kevin O'Leary has a warning for Gen Z founders wanting to work 18 hours a day: “How stupid is that?”

There is a type of startup success that looks like this: no sleep, no weekends, no social life, just pure, unrelenting grind. It looks good on paper, maybe even on a LinkedIn post. But Shark Tank investor and serial entrepreneur Kevin O'Leary wants young founders to know that version is a lie.

“The worst advice I hear young founders talk about all the time is that they want to work 18 hours a day. How stupid is that?” O'Leary said in a recent Instagram video.

That is not just an opinion of someone who has spent decades evaluating businesses and the people behind them. It’s a warning.


The myth of hustle that won’t die
The US has never really gotten rid of hustle culture. If anything, it has gained new energy. The 996 schedule, 9 a.m. to 9 p.m., six days a week, was outlawed in China in 2021, but Silicon Valley has started to wear it as a badge of honor. Last year, AI start-up Rilla warned potential hires not to apply if they were not prepared to work more than 70 hours a week.

It rings a bell for a generation of young Americans raised on hustle rhetoric, the Gary Vee clips, the Elon lore, the “sleep is for the weak” mantra. But quietly, science has been busting this myth for years.

A peer-reviewed study published in the Journal of Business Venturing found that sleep deprivation has a significant negative impact on an entrepreneur’s ability to evaluate new business ideas. Sleep-deprived founders were unable to reliably differentiate between high-potential and poor opportunities. The study surveyed over 700 entrepreneurs worldwide and conducted controlled experiments on sleep deprivation. “Entrepreneurs who consistently choose hustle over sleep, thinking that sleep comes after success, may be subverting their efforts to succeed,” said lead author Jeff Gish of the University of Central Florida.

In a nutshell, all-nighters don't make you smarter. They’re making you worse at the most important thing founders do: making good calls.

Your body keeps the score, and so do investors
O’Leary was direct in his Instagram caption: “If you show up looking half-dead, I'm not investing. You're not a hero, you're a liability.”

That framing is important. Investors don’t bet on ideas; they bet on people, and a founder who’s shot themselves in the foot is a liability, not an asset.

The health ramifications back this up. Harvard Health says that young people who are constantly under a lot of workload and time pressure are much more likely to develop major depressive disorder and generalized anxiety disorder. Chronic workplace stress also impairs the immune system and raises the risk of cardiovascular disease.

O’Leary is clear: sleep, exercise and eating well are not luxuries. They are the infrastructure. “This idea that you don't get any sleep, as if it's good for investors, is sheer stupidity," he said. “Eating well, getting sleep, and exercising are how you optimize.”

What O’Leary really wants you to pay attention to
Beyond the wellness argument, O’Leary has been consistent about where he thinks Gen Z founders should be focusing their energy and beyond: artificial intelligence. In March, he said that if he were in his 20s today, he would be focused on helping small businesses adopt AI tools or building data infrastructure.

“There's going to be a massive amount of people wanting to use it that don't know how to, and they're willing to pay to solve that pain point,” he said.

The opportunity is there, but you can’t build anything meaningful if you’re burnt out by month three.

Working smart, not just hard
O'Leary hasn't always been the poster child for balance. In a 2024 post on X, he wrote that success requires working “25 hours a day.” His advice is now a major shift, which more and more business leaders seem to be jumping on board with.

Insomnia Cookies CEO Seth Berkowitz takes two-hour breaks from his phone daily. Virta Health CEO Sami Inkinen takes off one week a year to disconnect completely. These are not people who have tuned out. It's people who have come to understand that recovery is part of performance.

It’s a distinction worth hanging onto for Gen Z founders trying to make it in a noisy, competitive landscape. Hustle is a thing. But running on empty doesn’t make you a founder worth betting on. That makes you a liability.

And Kevin O'Leary, for once, is not holding back his words about it.