A 72-year-long study conducted at Harvard tracked what really makes human beings happy. The study's longtime director, George Vaillant, when asked what has been learned, answered pointedly, "That the only thing that really matters in life are your relationships to other people."

In the last two decades, scientists have discovered that this truth is even wired into our brains. Researcher Daniel Goleman summarizes it this way: "The most fundamental revelation of [the discipline of neurobiology is that] we are wired to connect. Neuroscience has discovered that our brain's very design makes it sociable, inexorably drawn into an intimate brain-to-brain linkup whenever we engage with another person."