"Who am I?" This is a critical question for just about anyone, but it's especially important to the narrator of The Fault in Our Stars, Hazel Lancaster. After all, Hazel has the added complication of cancer—she doesn't have much time left to answer the question. Hazel's self-discovery is helped along by a boy, a book, and ultimately, herself.
Cancer changes a lot of peoples' identities in the book, including Hazel's and her parents' roles in the family.
Augustus wants so badly to achieve his goal of doing something big or heroic in his lifetime, but he should focus more on what he's already done.