The speaker wakes up hopeful, looking forward to seeing someone whose smile makes their heart race. The first stanzas feel light and easy: everything is fine, they're on time, and the only thing on their mind is that familiar face. The short, rhyming lines (the "strange day" and "going on my way" couplet, or "up beat" and "a tear or three") give the poem a bouncy, almost sing-song feel, which makes what follows hit harder.
Then the mood shifts. A teacher looks glum, classmates are crying, and the speaker, confused, asks what's happening. The poem never says outright what happened, but the final line, "you were gone," suggests the person they were waiting to see has died or left for good. The sunny setting, "into the morning sun," sits oddly against the news. The speaker's feelings move from happy anticipation to confusion to sudden shock, and the poem stops right there, leaving the grief unspoken.