“For eighty-four years (and counting), the Harvard Study has tracked the same individuals, asking thousands of questions and taking hundreds of measurements to find out what really keeps people healthy and happy. Through all the years of studying these lives, one crucial factor stands out for the consistency and power of its ties to physical health, mental health, and longevity. Contrary to what many people might think, it’s not career achievement, or exercise, or a healthy diet. Don’t get us wrong; these things matter (a lot). But one thing continuously demonstrates its broad and enduring importance: Good relationships. In fact, good relationships are significant enough that if we had to take all eighty-four years of the Harvard Study and boil it down to a single principle for living, one life investment that is supported by similar findings across a wide variety of other studies, it would be this: Good relationships keep us healthier and happier. Period.”