A lifetime isn't long enough for the beauty of this worldand the responsibilities of your life. (12.11-12)
By this point in the poem, it seems pretty clear that our speaker is all about the beauty of this world. And we're guessing that she finds most parts of the natural world beautiful, even parts that most people might not. What then are these responsibilities that we won't have time for if we focus on the beauty of the world? Maybe she's referring to the responsibility we feel to mourn what has been lost.