Warren Buffett has given us plenty of sound advice over his lifetime. The greatest investor of this generation has amassed a following of millions who've learned, like Buffett, that long-term success is achieved by making smart investment decisions.

When making those smart decisions, what assets should you be investing in the most? Warren Buffett has a simple answer to that question, and it's not what you think.  

In a 2019 interview with Yahoo Finance editor-in-chief Andy Serwer, Buffett said:

By far the best investment you can make is in yourself.

He added that investing in developing your communication skills -- both in writing and in-person -- "can increase your value by at least 50 percent."

Don't stop learning.

What I gather from having followed Buffett is that to make the most of your investment, you should never stop acquiring knowledge -- the kind of knowledge that betters yourself as a whole person, not just as an investor.

Buffett's lifelong pursuit of learning, which he shares with his longtime Berkshire Hathaway partner and colleague Charlie Munger, is the secret sauce of their success. Munger once said:

Warren Buffett has become one hell of a lot better investor since the day I met him, and so have I. The game is to keep learning, and I don't think people are going to keep learning who don't like the learning process.

Most people think learning stops once you acquire degrees and certifications. Life should be about continuous learning, and there are many other ways to do it. 

Learn by surrounding yourself with the right people.

Buffett spoke with some college students a few years back and said, "You will move in the direction of the people that you associate with. So it's important to associate with people that are better than yourself."

As the famous saying goes, we are the average of the five people we spend the most time with. Make sure to associate with those further along the path who can potentially help you to learn new things, grow, and advance your career. 

Learn by eliminating your bad habits.

One classic piece of Warren Buffett advice may be a good starting point to your learning process: Overcome the bad habits that may be keeping you from achieving your full potential. Buffett once said, "I see people with these self-destructive behavior patterns. They really are entrapped by them."

He advised graduating students at the University of Florida to learn and practice good habits early on before it's too late. "You can get rid of it a lot easier at your age than at my age, because most behaviors are habitual," said Buffett.