Well you know how is younger brother died to cancer? Well he feels that if anyone deserved to die it was him, because he is less personable and intelligent then his little brother was. He's pretty disturbed by the whole situation, and because he is so immature for his age and mental state can really only relate to younger people. That's why he loves his little sister so much. Anyways, because he feels guilty for living, and has such a connection with children, all he wants to do is protect them. That is why in the novel he washes away the graffiti with swear words on it, since kids could see it. He dreamily talks about how he doesn't know what he wants to do with his life, but if he could do anything he would watch the children play in the fields of rye, and if one fell he could save them, catch them. That's why the book is called The Catcher in the Rye. I hope that makes sense.
