Happiness is an elusive and subjective concept. Gretchen Rubin, best-selling author, co-host of the popular podcast Happier with Gretchen Rubin and one of the leading experts on habits and happiness, says rather than trying to define or imagine what it looks like, we should focus on building it in our individual lives. After all, studies who 40 percent of happiness is in our control, in our conscious thoughts and actions. In this interview with SUCCESS contributing editor Mel Robbins, Rubin stresses how important relationships are to building happiness. Plus, learn Rubin's four habit tendency types - Upholder, Obliger, Questioner and Rebel - and learn the ways your type affects how you react to inner and outer expectations.