So it's not surprising the business titans agree that who you spend time with matters.
By choosing the right group of friends, you can push yourself to achieve bigger professional goals, Buffett and Gates say.
"You will move in the direction of the people that you associate with," says Buffett, who recently addressed a group of students at Columbia University along with Gates.
"It's important to associate with people that are better than yourself."
Gates says your social circle is an important investment of time and energy.
"Some friends do bring out the best in you," the Microsoft co-founder says, "and so it's good to invest in those friendships."
Besides one another, they each keep an impressive circle of friends. Gates is pals with Virgin Group founder Richard Branson and Oracle co-founder Larry Ellison while Buffett is friends with Charlie Munger, VP of Berkshire Hathaway, and Mark Cuban.
"You want to associate with people who are the kind of person you'd like to be," Buffett says.
In other words, invest your time like you would your money: Wisely.
Check out what Gates and Buffett say they would do if they had to start their careers over