In so many ways, our lives are easier than ever. We're sheltered from the elements our ancestors braved daily. We don't need to grow, hunt, or gather our food, nor do we ever need to feel hungry for more than a few hours. We can immerse ourselves in digital entertainment that stimulates us in ways our great grandparents never could have imagined. And yet we're unhappy. There were over 45,000 suicides and over 100,000 drug overdoses in America...