Celestie777 retells the sun and moon's relationship as the world's oldest love story. The moon is shown as shy: she admires the sun, blushes, and hides whenever he rises. He, in turn, lights up the whole world as if he's searching for her. But they are made for different halves of the day, so she stays lonely and set apart, and the speaker sees this as true love that is always present yet never close, "always behind but never beside."
The speaker sounds tender and a little sad, but also accepting. The last stanza adds a twist: the two are "too comfortable" in their own realms to leave them, and twilight carries messages between them. If they ever did meet, it would cause an eclipse, so their distance seems to protect something. The mood is wistful and quietly romantic, with love presented as devotion that survives separation rather than a story about being together.