How the 3-part structure and sound and poetic devices enhance meaning of "Coy Mistress"

Andrew Marvell in "To His Coy Mistress," expresses his love and passion for his mistress; however, he also emphasizes the limitations that time has placed on their love.  Therefore, he states that they must make the most out of their relationships within its boundary of time.  In lines 1-20, the writer speaks in the conditional.  He states that in a perfect world, they could do whatver they pleased without worrying about time; however, line 21-32 play a pivotal role.  This portion of the poem servesas a reality check, emphasizing the withering constraints of time.  Then, from lines 33-46, the writer expresses the urgency of their relationship.  He states that they need to do everything they can before time runs out.