A self-made millionaire who studied 1,200 wealthy people found there's one thought pattern they all tend to avoid

"People who believe their best days are behind them rarely get rich, and often struggle with unhappiness and depression," Siebold writes in "How Rich People Think."

"Self-made millionaires get rich because they're willing to bet on themselves and project their dreams, goals, and ideas into an unknown future."

This future-oriented mindset does not mean they completely neglect the past, Siebold emphasizes: "They appreciate and learn from the past while living in the present and dreaming of the future." And they don't just dream - they spend years tirelessly and patiently planning in order to realize their dreams.

Part of this ability to avoid nostalgia and look towards an unknown future comes from their comfort with uncertainty. They're not only willing to step outside of their comfort zone - they expect to.

"The great ones know there's a price to pay for getting rich, but if they have the mental toughness to endure temporary pain, they can reap the harvest of abundant wealth for the rest of their lives," the self-made millionaire says.