The poem sets two places side by side: the peak and the swamp. From the peak, the speaker sees the whole valley of human life, and the right response is "pity and joy," a mix of feelings rather than a single one. In the swamp, where you can't see far, you simply "follow the stars." The last stanza returns to this pattern but sharpens it. The valley is now "teeming earthly life, birth and death," and the swamp advice becomes "love all."
The middle stanzas shift to light. Natural light loves things as they are, "kit & caboodle," in storms and calm alike. The French phrase for artificial light, "Lumiere d'artifice," suggests something more selective, carving out shapes and etching detail, like a photographic plate. The speaker seems to value both, but natural light's unconditional quality feels like the model for the poem's final line.
The mood is calm, accepting, and quietly uplifting, with a sense of wide, patient compassion.