The poem is structured around a series of contrasts between the lark and the speaker. The lark is free to fly and sing in the sky, while the speaker is bound by the earth. The lark's song is pure and clear, while the speaker's voice is "harsh" and "discordant." The lark is filled with joy and ecstasy, while the speaker is filled with sorrow and despair.
These contrasts emphasize the speaker's longing for the freedom and happiness of the lark. She yearns to escape from the constraints of the physical world and experience the joy of soaring through the sky. The lark's song becomes a symbol of this yearning, and the speaker is inspired by it to believe that she, too, can one day transcend her limitations and find freedom.
Millay's poem is a powerful and moving meditation on the human spirit's capacity for transcendence. It is a reminder that even in the midst of darkness and despair, there is always hope for beauty and freedom.