Standing high on the Sussex Downs, the speaker sees birds crossing the open sky, the distant sea glittering, and the Sussex Weald spreading north below her like a kingdom. The landscape gives the moment a feeling of space and elevation. She says she was happier than the larks that nest there and sing upward — even the birds in flight were not as happy as she was.
The last stanza turns inward. Someone close to her is near, and good to see and hear, but the happiness does not come from that person, from the earth, or from heaven. It comes from herself: “It was myself that sang in me.” The real subject is not the scenery but a sudden, clear sense of inner joy — a happiness that feels as natural and buoyant as birdsong, rising from within.