As the educator who previously answered this question mentioned, Neruda uses repetition—or a "refrain"—to create a sense of mournful suffering throughout the poem. 

Additionally, Neruda uses personification to dramatize the theme of heartbreak. He personifies the night sky in the second and third stanza, giving it actions that are normally attributed to humans: "the blue stars shiver," "night wind revolves in the sky and sings." This picture of night becomes the backdrop against which Neruda recalls his love and how he "kiss[es] her again and again under the endless sky." 

Simile is present later in the poem when Neruda comments that "the verse falls to the soul like dew to the pasture"; here, Neruda is comparing his lines of poetry being heard or read by a human soul to the condensation of water on grass in the morning. 

Finally, Neruda uses hyperbole to emphasize the qualities he likes best about his former lover: namely, her "infinite eyes."