In Denis Johnson's novel "Tree of Smoke," the quote "If illness didn't kill you, you died of bad luck" reflects the harsh realities faced by the characters during the Vietnam War era. This statement encapsulates the unpredictability of life and death in a conflict-ridden environment, suggesting that survival hinges as much on fortune as on health. It conveys a sense of fatalism, emphasizing how circumstances beyond one’s control can dictate outcomes. As characters navigate the chaos of war, their fates are often intertwined with chance.

This quote also highlights the broader existential themes present in the narrative, where individuals grapple with the randomness of suffering and survival. The notion of 'bad luck' resonates as characters confront various forms of violence, illness, and despair, underscoring the fragile nature of life. Johnson's exploration of these themes invites readers to reflect on the complexities of human existence, where even the resilient may succumb to the unpredictable tides of fortune.