Two years ago, Eric Greitens unexpectedly heard from a former SEAL comrade, a brother-in-arms he hadn't seen in a decade. Zach Walker had been one of the toughest of the tough. But ever since he returned home from war to his young family in a small logging town, he'd been struggling. Without a sense of purpose, plagued by PTSD, and masking his pain with heavy drinking, he needed help. Zach and Eric started writing and talking nearly every day, and Eric set down his thoughts on what it takes to build resilience in our lives. Eric's letters drawing on both his own experience and wisdom from ancient and modern thinkers are now gathered and edited into a timeless handbook. They explain how we can build purpose, confront the pain in our lives, practice compassion, develop our vocations, find a mentor, create happiness, follow a role model, think about the story of our lives, and much more. Resilience grapples with real hardship. The lessons are deep, yet practical, and the advice leads to clear solutions. This is a profoundly hopeful book: We all face pain, difficulty, and doubt. But with resilience, we can lead vital, flourishing lives.