The speaker looks up at the sky at 7:41 pm and sees something small but striking: the moon already halfway up while the sun is still setting. For a brief moment, both are visible, each lingering a little longer to be near the other. The speaker imagines them as lovers who are always chasing each other and never quite meeting.
The poem also points out that a real meeting would be a disaster. If the sun and moon truly collided, the world would suffer, so their love only works because they stay apart. That's where the speaker turns the image toward themselves, calling it "romantically sad" that their own love is best described this way.
The mood is wistful and tender, with a quiet ache underneath. The speaker doesn't sound angry. They seem to accept that closeness is possible only in passing moments, and that being almost together is both beautiful and painful. The run-on lines, with their repeated "as long as they could," make that longing feel breathless and reluctant to end.