Having endured and overcome many difficulties, Helen Russell has researched sadness from the inside out for her entire life. But by allowing ourselves to experience pain, she found, we learn to truly appreciate and embrace joy. Interweaving Helen's personal testimony with the latest research on sadness—as well as the experiences of writers, comics, athletes and change-makers from around the world—this vital and inspiring guide explores why we get sad, what makes us feel this way, and how it can be a force for good.