Have you ever walked through a park on a sunny spring day when everyone looks like they're having a great time and thought, gee, I wish I were that happy? Have you ever perused Facebook and seen a group of friends beaming into the camera and wished that your life could be as good as theirs? Have you ever felt like your life would be so much better if only you had more money? Or a boyfriend? Or a new car? Or a PhD? Or simply a nice cold beer? Well, my friend, you are not alone.

Ever since Thomas Jefferson wrote in the Declaration of Independence that man has the right to "life, liberty, and the pursuit of happiness" (and we'll pretend that he didn't just mean rich white men), the American people have made it their mission to find happiness. And we aren't alone, either. Even if it isn't written down in one of their country's most important historical documents, people from pretty much every nation in the world is looking for that magic combination that will make them happy. But what is the perfect recipe for happiness? And how do we define happiness to begin with?