Warren Buffett is one of the richest people in the world, but money isn't a factor when it comes to measuring the quality of his life. In 2017, when Buffett and Microsoft co-founder Bill Gates shared the stage for a talk at Columbia University, one student asked: "Are there any major life lessons that you two have learned about relationships through your personal experiences?" "Well, it's a very important question. You will move in the direction of the people that you associate with," Buffett answered. "So it's important to associate with people that are better than yourself."

'The ultimate test'

Buffett, who just turned 89 on Saturday, August 30th, 2019, has given similar advice in the past. "Basically, when you get to my age, you'll really measure your success in life by how many of the people you want to have love you actually do love you," he said in 2001 during a speech at the University of Georgia. "I know people who have a lot of money, and they get testimonial dinners and hospital wings named after them. But the truth is that nobody in the world loves them," Buffett continued. "If you get to my age in life and nobody thinks well of you, I don't care how big your bank account is — your life is a disaster. That's the ultimate test of how you have lived your life."

Choose your life partner wisely

Out of all the people who love you back, the most important person by far, according to Buffett, is your spouse. "I can't overemphasize how important that is," he said in his 2017 conversation with Gates. In the 2017 HBO documentary "Becoming Warren Buffett," the billionaire said that he owes some of his greatest qualities to his first wife Susan. "I just got very, very, very lucky. I was a lopsided person. And it took a while, but she just stood there with a little watering can and nourished me along and changed me," he recalled. In many ways, Susan did help Buffett become the man that he is today: She got him interested in civil rights, feminism, encouraged him to become more of a public figure and to donate more of his money during his lifetime.

If you get to my age in life and nobody thinks well of you, I don't care how big your bank account is — your life is a disaster. Warren Buffett CEO, Berkshire Hathaway

While they never got divorced, Susan moved away from Omaha and the two remained very close, according to the documentary. She also helped orchestrate Buffett's relationship with Astrid Menks, whom he married after she died. (Buffett and Astrid tied the knot on August 30, 2006, the same day he turned 76 — and have since been together for 13 years.)

Bill Gates agrees with Buffett

In their conversation at Columbia University, Gates, who has been a longtime friend of Buffett's, said that "some friends do bring out the best in you, so it's good to invest in those friendships. It's really through Melinda and seeing other people that I realized, okay, it's really worth the investment to have those people, as you're always there to help them and vice versa." Gates also commented on his marriage with Melinda last year, in a Facebook Live talk: There's a certain type of intensity when you're raising a family together, said, "but we're very lucky because we mostly see things the same way. Our goals are very much the same."

It takes all kinds