The e-mail, workout and sleep habits of highly successful billionaire Mark Cuban

Mark Cuban checking his phone
Photo credit Chip Somodevilla

Tech billionaire Mark Cuban says he conducts business almost exclusively via email. To be constantly connected, he carries two phones: one Android, one iPhone.

"With access, I'm always available; I can always communicate," says Cuban. As owner of the Dallas Mavericks, a star on ABC's "Shark Tank" and an investor in countless companies, that's a lot of emails. All the time.

In a recent episode of The Thrive Global Podcast, host Arianna Huffington asked Cuban if the constant flood of unanswered emails ever leaves him feeling overwhelmed.

"I guess I go through so many emails, I've kind of become immune to that," says Cuban.

He checks emails whenever he has an extra minute. "If I'm laying in bed watching a game, if it's halftime of a Mav's game, that's when I'll do my emails," says Cuban. "It allows me to disconnect from whatever other things that have my attention, and it actually works out really well."

Still, Cuban says he is actually less attached to his devices now, at 58, than he used to be.

"I think entrepreneurs go through a process. When I was all in and I was starting companies, I would dream about work. And literally, I'd wake up and I'd have to do things ... it just consumes you," says Cuban. "And I think entrepreneurs go through that process; creative people go through that process.

"As I kind of graduated to a different facet of my life, I really don't have a problem disconnecting because there's nothing that's so pressing," he says.

"Before I go to bed, I can put my phone [down] and not worry about having to pick it up in the middle of the night and [I can] just get a good night's sleep."

Or he can watch NBC's "Law & Order." Cuban says he uses headphones to watch TV, so as to not disturb his wife, and sets the television to turn off automatically so he can just fall asleep.

Mark Cuban: AI will produce the world’s first trillionaires
Mark Cuban: AI will produce the world’s first trillionaires

"Maybe it's a bad habit," Cuban says of his TV routine. "I think it's an old habit that I just haven't gotten rid of. Where, when my mind was racing so much and I needed to turn off and couldn't, it was a distraction. When I was thinking about work all the time. If there was something else on, just to distract."

He says he also uses a fitness tracker to know when he's getting good sleep and when he's not. (He's used Fitbit but says the Microsoft version is his favorite.)

Cuban says he gets by on six hours of sleep a night, though seven is ideal, and he's always down for a good nap particularly if he is traveling.

Why this investor eats canned fish for breakfast
Why this investor eats canned fish for breakfast

He also works out for an hour every day. "That I will find a way to get [a workout] done, I think, reflects how relentless I can be in the business world as well," Cuban says.

Besides, that all still leaves plenty of time for e-mail.

"If I'm sleeping six, seven hours and working out one hour, there's another 16 hours that I have access to my phone," he says.

See also:

How Mark Cuban went from a working-class family in Pittsburgh to a self-made billionaire

Mark Cuban: 'When you're 22, 23, 24, there's no such thing as failure'

Mark Zuckerberg, Richard Branson and Mark Cuban all agree that this one habit is key to success

Disclaimer: CNBC owns the exclusive off-network cable rights to "Shark Tank."

Mark Cuban’s best advice for college grads
Mark Cuban’s best advice for college grads