Gretchen Rubin (@gretchenrubin) is a Three-time #1 New York Times bestselling including "The Happiness Project" and most recently, the just released book "The Four Tendencies: The Indispensable Personality Profiles That Reveal How to Make Your Life Better (and Other People's Lives Better, Too)." She also hosts a podcast called "Happier with Gretchen Rubin." Listen in as she and Mark talk about the four tendencies that she's identified and how they affect our Unbeatable Mind. Learn how to use your own tendency to make it easier to motivate yourself.