The quote from Ian McEwan's "Saturday" captures the dual emotions of parents whose children have recently reached adulthood. On one hand, there is a sense of pain as parents observe the rapid shift in dynamics, where their children become more independent and less reliant on them. This transition can create a feeling of loss, as the comforting dependency of childhood gives way to a more distant relationship.

On the other hand, the term "ruthless" highlights how these young adults often move on without hesitation, embracing their newfound freedom. While parents may cherish the memories of their children's dependence, they also face the bittersweet reality that their children are growing up and carving their own paths, sometimes forgetting the support they once relied upon. This reflects the challenging nature of parenting as children evolve into autonomous individuals.