The afternoon knows what the morning never suspected.

Read as an aphorism, the line suggests that experience accumulates unevenly across the day (and by extension across a life): what seems clear or settled in the “morning” can be revised by what happens later. “Afternoon” stands for the knowledge that comes from having lived through events, consequences, and surprises that were not imaginable at the outset. The phrasing implies humility about plans and first impressions, and it also carries a quiet optimism: later stages can bring insight unavailable earlier. Even without a verified Frost source, the sentiment aligns with a common modernist preoccupation with time, change, and the limits of foresight.