Mark Cuban may have a reputation for being unapologetic, but he’ll be the first to admit that he has plenty of regrets.

One of the things Cuban says he’s struggled with during his career is constantly pushing himself to work harder than everyone around him.

"You’ve got to grind to be successful and my regrets have come from [times when] I didn’t grind hard enough or maybe there was somebody out there outworking me," Cuban says. "That’s just not acceptable."

For Cuban, whether you’re a billionaire or just starting your first company, effort is the one thing in business you can control.

"I didn’t control it as much as I needed to and there have been times when I regretted that," he says.