The speaker keeps imagining being something else. First comes a leaf blown from branch to branch, then a bird scattering its scent through the air. Next the wishes turn human: a rich man who can go wherever he likes, and a "mature spirit" who travels the world. Each wish is about movement and freedom, a longing to escape being fixed in one place.
Then the poem turns on the word "However." Now the speaker wishes to be an idiot who needs only bread to live. After all that wandering, the final wish is for the opposite: a life with almost no wants. The poem seems to suggest that wealth, wisdom and freedom to roam bring their own burdens, and that not knowing or needing much might be a kind of peace.
The mood is wistful and a little restless, with a gentle irony at the end. The short, simple lines make the speaker sound honest and tired of wanting so much.