The quote from Ian McEwan's "Atonement" conveys a powerful reminder of the unpredictability of life. It suggests that even when one feels invincible and in control, circumstances can shift dramatically. The world is not always forgiving, and what feels secure can quickly become precarious. This reflects the theme of vulnerability that permeates the novel.

The phrase emphasizes the importance of humility and awareness of life's transience. It serves as a cautionary note that even in moments of triumph, one should remain grounded, as fortunes can change unexpectedly. McEwan's work often explores such complexities of human experience, highlighting the fragility of happiness and the potential for downfall.