Buffett addressed the topic during a 2017 conversation with Bill Gates at Columbia University, too. "You want to associate with people who are the kind of person you'd like to be. You'll move in that direction," he said. "And the most important person by far in that respect is your spouse. I can't overemphasize how important that is."
That's life advice the 87-year-old has been emphasizing for years. As he said at the 2009 Berkshire Hathaway annual meeting, "Marry the right person. I'm serious about that. It will make more difference in your life. It will change your aspirations, all kinds of things."
Research agrees that who you marry can significantly affect your level of success. People with supportive spouses are "more likely to give themselves the chance to succeed," according to a study published by psychologists from Carnegie Mellon University.
Another study by Brittany C. Solomon and Joshua J. Jackson of Washington University in St. Louis shows that having a conscientious spouse can boost your salary by $4,000 per year and increase your chances of getting promoted.
"Significant others can help you thrive through embracing life opportunities," Brooke Feeney, lead author of the Carnegie Mellon study, tells CNBC Make It. "Or they can hinder your ability to thrive by making it less likely that you'll pursue opportunities for growth."
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Don't miss: These psychologists say that the secret to your success is who you marry