Sheryl Sandberg is the Chief Operating Officer of Facebook. Two years ago, her husband Dave Goldberg suddenly died at age 47. She founder herself in a dark place, but had to figure out how to live in this new reality — "Option B" — without him. Sandberg spoke with us about how you can build resilience like a muscle, how she overcame her darkest days, how Mark Zuckerberg has helped her through, and why companies should think of sick leave, the same way they think of maternity or paternity leave.