World's richest woman Gina Rinehart is enduring a media firestorm over an article in which she takes the "jealous" middle class to task for "drinking, or smoking and socializing" rather than working to earn their own fortune.

What if she has a point?

Steve Siebold, author of "How Rich People Think," spent nearly three decades interviewing millionaires around the world to find out what separates them from everyone else.

It had little to do with money itself, he told Business Insider. It was about their mentality.

"[The middle class] tells people to be happy with what they have," he said. "And on the whole, most people are steeped in fear when it comes to money."