The speaker looks back on a childhood when the sun and moon were playmates. Watching from a moving car or on wheels, they imagined hide and seek with the sun and a race against the moon, even sticking out their tongue as they "won." Friendship felt just as easy then.
As the speaker grew older, friends drifted away, and the speaker began feeling things deeply and writing them down. The sun and moon changed too, becoming a glorious muse and a regal queen instead of games to play. The speaker wonders whether the friends left because of who they were becoming, or simply moved on, and whether "innocent simplicity was the cost of complex poetry."
The mood is wistful and a little lonely. The speaker doesn't fully regret the change, since the images of gold, blue, purple and silver still glow vividly. Yet the last line, calling their own assumption of glory "foolish," leaves a sense of doubt about what was gained and what was lost.