A huge symbol in The Fault in Our Stars is Augustus's cigarettes. Augustus has a habit of putting a cigarette between his lips, but he never lights it saying, "They don't kill you unless you light them. And I've never lit one. It's a metaphor, see: You put the killing thing right between your teeth, but you don't give it the power to do its killing." In a way, Augustus is taunting cancer (if cancer was a living, thinking thing) being like, "I'll put the killing thing into my mouth, but you have no power over me anymore!" It's sort of a way for him to celebrate that his body is no longer a slave to cancer.