How does Q's dealing with the end of high school give him insight into Margo?

Reading Whitman, Q is convinced that he has to "become" Margo to find her. At the same time, Q is experiencing the "lastness" of school, doing many things for the last time. He finds it hard to leave school but that once he makes the decision easy. In leaving, Q feels like he finally understands Margo. She is not coming back. She gave up her roots and it felt too good