Holden is telling you his story and, through this exercise, he is able to come to a certain level of understanding about his well being. He describes his sickness as "this madman stuff that happened to me." At the end of the narrative he comes closer to full grips with his situation, "... how I got sick and all". The reader should see certain patterns in the extemporaneous nature of his narrative. He thinks about things in a patterned way, though these intrusive thoughts seem to be random. All of his ramblings are rooted in the anxiety that causes his breakdown.