The No. 1 Key to a Happier, Longer Life—‘that younger people don't know, according to the oldest and ‘wisest’ Americans

I once interviewed Karl Pillemer, the Cornell sociologist and author of “30 Lessons for Living: Tired and True Advice from the Wisest Americans.” He’d seen numerous studies showing that people in their 70s, 80s, and beyond were far happier than younger people. He was intrigued: “I keep meeting older people — many of whom had lost loved ones, been through tremendous difficulties, and had serious health problems —