Rubén Darío published this poem in Cantos de vida y esperanza (Madrid, 1905), the book where modernismo stops showing off and starts settling accounts. Darío was thirty-eight. The whole collection is written from the point where youth can finally be looked at from outside.
The structure is a refrain and a procession. The quatrain beginning Juventud, divino tesoro — youth, divine treasure — comes back again and again, unchanged, and between one return and the next a woman passes, and another, and another: each one a stretch of the speaker's life, none of them staying. The refrain never comments on what happened in between. It just returns, and in returning measures how much is gone.
What saves the poem from pure lament is its last line. After nine or ten stanzas of counting down, the speaker does not close on the loss: he closes by claiming something that has not been taken from him yet. That single-line turn is why the poem is still recited from memory more than a century later.
The verse is kept in Spanish. Translating it in passing would replace the work with a paraphrase of it.