Sheryl Sandberg’s essay on grieving, written this week after she emerged from the 30-day Jewish mourning period known as “shloshim,” has gone viral. People worldwide have admired the Facebook COO’s candor in the wake of the sudden death of her 47-year-old husband, Dave Goldberg. But what happens during shloshim that made Sandberg begin her piece: “I have lived thirty years in these thirty days. I am thirty years sadder. I feel like I am thirty years wiser”?