Respuesta :
I think the answer is that life is filled with disappointment, so the first one
life is fleeting
In the excerpt he's talking about how the swans are beautiful on the water. He reflects on what they do at the lake's edge. But not at his lake any more...he thinks about what they will do at another lake or pond edge. He's showing how things come and go, but he is not melancholy for the swans. He's just acknowledging that they move on.