We all know people who greet every new day with a big smile and lots of positive, can-do energy, regardless of the anxieties, stresses, problems, and obstacles that may be looming. A growing body of research suggests having zest can result in greater success; greater happiness and well-being; better physical and mental health; and larger, stronger, and more sustaining social networks. Teens who learn the habit of zest have been shown to perform better...