After selling the software business he started in his basement to the Mattel Toy Company for $3.7 billion in 1999, Kevin O'Leary went on to start his own mutual company, O'Leary Funds. Today, he's chairman of O'Leary Funds, on the board of The Richard Ivey School of Business and a star on ABC's hit show, "Shark Tank." He also has a and a primarily online wine business, Kevin O'Leary Fine Wines and for a while he was running for political office in Canada, too.
Suffice it to say, O'Leary has got a lot to manage. So how does he stay on top of everything?
Post-its notes and a pen.
And he recommends others implement his strategy if they are trying to juggle competing priorities.
At the end of each day, O'Leary writes down the three most important tasks for the next morning on a "sticky note, you know, just a yellow piece of paper," says O'Leary in a recent Facebook live. Then, the next day, you complete those three tasks before you do anything else.
"Three really important things. Maybe it's medical appointment you have to do, obviously, or it's something at work but it is three things that consume time," says the investor and entrepreneur.
"And you don't take any emails, you don't take any phone calls, you don't do anything else until you have got the three things done," says O'Leary.
"That really works. Trust me, I do it every day."
O'Leary takes Sundays off, but every other day, including Saturdays, he takes this post-it-note approach to organizing his day.
"It makes you immensely productive. Try it. It's a fantastic trick. You don't need any technology for that. You just write it down on a piece of paper," he says.
For entrepreneurs in particular, managing your day is critical, because building a business takes a lot of time and energy.
"Business is really hard. Most entrepreneurs that start the journey think they are going to be an overnight success and make a billion dollars in 12 months. That virtually never happens," he says. "The majority of entrepreneurs that are successful have done it over eight, nine, 10 years. They have built a franchise over time, and that's what matters. You have got to get ready to sacrifice, you have to be ready to spend a tremendous amount of time and energy away from friends and family," says O'Leary.
If you are going to be putting in long hours, spend your time the most efficient way possible —thanks to O'Leary's Post-it trick.
Disclaimer: CNBC owns the exclusive off-network cable rights to "Shark Tank."