Kelly McGonigal, Ph.D., is a health psychologist who specializes in understanding the mind-body connection. She is the best-selling author of The Willpower Instinct and The Upside of Stress. Her latest book, The Joy of Movement, explores why physical exercise is a powerful antidote to the modern epidemics of depression, anxiety, and loneliness. For more information, go to her website: http://kellymcgonigal.com.