"With her mega-bestseller Quiet, Susan Cain urged our society to cultivate space for the undervalued, indispensable introverts among us, thereby revealing an untapped power hidden in plain sight. Now, she employs the same mix of research, storytelling, and memoir to explore why we experience sorrow and longing, and the surprising lessons these states of mind teach us about creativity, compassion, leadership, spirituality, mortality and love. Bittersweetness...