The news that Augustus's cancer has returned reverses his and Hazel's roles in their relationship, and it causes Hazel to reevaluate her opinion on getting close to others. Until now, Hazel has been the “grenade,” meaning the one who would hurt everyone around her when she died. Her fear of hurting others has led her to wonder if it's best to maintain her distance from people in order to spare them pain when she finally succumbs to her cancer. It's the reason she initially hesitated to be anything more than friends with Augustus. Augustus's news, however, suddenly makes him the grenade in their relationship, since his death is almost certain to come before hers, and Hazel is forced to view him the way her loved ones view her. With the change in their roles, she immediately realizes that she can't keep from hurting people when she dies, and that perhaps she shouldn't want to. She recognizes that, even though it will be painful when Augustus dies, she wouldn't want to love him any less. This epiphany suggests that Hazel shouldn't want those around her to love her any less, and she shouldn't keep people at a distance to avoid hurting them later.
The period following Augustus’s confession further emphasizes the distinction between “Augustus” and “Gus” in Hazel's eyes. From the time Augustus breaks the news to Hazel until just afterward as they talk about the idea of battling cancer, Hazel refers to Augustus by the full version of his name. This version of Augustus represents the dramatically heroic side of Augustus's character. He talks about the fact that there are no paintings glorifying death by illness in the Rijksmuseum, and Hazel holds up this “Augustus Waters,” even adding in his last name, to contradict Maslow's Hierarchy of Needs. But later, beginning with their flight home, Hazel switches to referring to him exclusively as Gus. The change in his name suggests a change in the way Hazel is thinking of him. The version of Augustus who Hazel calls “Gus” isn't the grandiose persona, but the relatively ordinary teenage boy who actually admits to feeling fear and struggles with his cancer. It is the version of Augustus with all the walls broken down.
Augustus handles talking to others about his cancer's return in a few different ways. Initially he hides it from Hazel. He doesn't fully explain why, but he hints that it's because he didn't want her to look at him differently, particularly during their trip. After he tells her, however, the conflict he feels over how to act in front of her becomes clear. Hazel describes him breaking down and sobbing just after he tells her, but almost immediately he composes himself and tells Hazel he'll fight the cancer. He even says he'll be around for a long time. Rather than let Hazel see how overwhelmed he feels, he again shows his bent toward heroism. From that point forward, at least through the rest of the section, Augustus generally uses humor to defuse the tension caused by the knowledge that he's dying. He tells Hazel, and then later Isaac, that he's “on a rollercoaster that only goes up,” and he seems to refuse to let his fear and sadness show in front of Isaac. The approach acts as a way for him to take some of the strain out of his situation, allowing him to avoid uncomfortable feelings and making it a little easier for him to interact. Even so, as the section ends, he brings up the subject of his death in a more serious way with Hazel. Watching the children play at the Funky Bones park, he tells her last time they were there he identified with the children, but now he identifies with the bones.
Hazel's thoughts about Maslow's Hierarchy suggest that people's needs don't fit in a neat pyramid as Maslow hypothesized. First, it's worth noting that Hazel's argument against the hierarchy—that according to it she shouldn't be able to concern herself with love and art because her health isn't secure—is debatable. She isn't in immediate danger of dying of her cancer, or dying of exposure or starvation for example, so one could argue that her most basic physiological needs are met. Regardless, she holds up Augustus as proof that the hierarchy is wrong because it's evident that thoughts of purpose and meaning are perhaps even more important to him because his death is imminent. As Hazel puts it, his “existential curiosity” was far greater than that of his “well-fed, well-loved, healthy brethren.” The implication is that questions of purpose and meaning about life aren't secondary needs. Instead they're basic needs that coexist alongside our fundamental physiological needs, like those for food and shelter.