How does Max’s life give Liesel purpose?

Max is a fighter. Max was a fist-fighter growing up, and as a teenager he resolves not to die without a fight. Max is wracked with anguish and guilt over leaving his family to save himself, but he comes to befriend Liesel as the two share their respective nightmares. Their friendship grows very deep, and Liesel reads to Max every night when he falls comatose. Max is an inspiration to Liesel. He wants to fight the evil and, while sick, Liesel and Max share stories to inspire them. Max eventually leaves so as to keep the Hubermans and Liesel safe. Liesel vows to fight the darkness armed with the momory of her friend.