Why do we hurt, feel self-doubt and constantly struggle throughout life? What does it take to overcome all the obstacles? The bottom line is that hardship is a part of life, but only by facing up to it and learning to tackle all of life’s challenges will we achieve our full potential. So how do you do that? With resilience.

Author Eric Greitens, in his correspondence with fellow Navy SEAL veteran Zach, tries to find the qualities, practices, and training needed to become resilient against the harder parts of life. His search took him through history, philosophy, and beyond. Ultimately, it seems the ancient struggle we face as humans has a solution that’s equally ancient.