In Cormac McCarthy's "No Country for Old Men," the quote emphasizes the complexity of self-perception and the challenges of understanding one's true nature. It suggests that self-awareness is a lifelong endeavor, indicating that the journey to truly know oneself is both difficult and ongoing. Even with effort, individuals may still misinterpret their own identities, implying that certainty about oneself is elusive.

This perspective reflects a broader theme in McCarthy's work, where characters often grapple with moral ambiguity and the consequences of their actions. The quote serves as a reminder that self-discovery is fraught with uncertainty, and that humans may never fully grasp their own motivations and weaknesses, underscoring the intricate nature of the human condition.