I interviewed 21 self-made billionaires about their secrets to wealth and success-here's what I learned

There are billions of people in the world, and only a tiny fraction of billionaires . These are the people who have created phenomenally successful businesses and changed the world in significant ways.

What's their secret to achieving such impressive accomplishments? What are their belief systems? What gives them the energy to pursue ambitious goals? How did they get to where they are today, and how can we embark on the same journey?

To answer these questions, I spent five years conducting face-to-face interviews with 21 self-made billionaires - which I also document in my new book, "The Billion Dollar Secret."