Gretchen Rubin is the New York Times bestselling author of several books about happiness, habits, and human nature. Her books have sold over 3.5 million copies worldwide, and Gretchen also has a popular blog and podcast, called Happier. Previously, she received a law degree from Yale and clerked for U.S. Supreme Court Justice Sandra Day O'Connor.  Topics in this episode include happiness engineering, how to make and break habits, willpower, and clutter.