That Faltzer Ain't One of Ours

I've just finished reading J.D. Salinger's literary success, The Catcher in The Rye today (inclusive to my other classmates as well,) after reading every chapter from every page from every paragraph from every word from every sentence. However the ending is very cryptic for the most part, and as a homework assignment today, I was to answer one question asking for some sort of explanation to the ending. However, I myself was completely puzzled as to what I was going to give as an answer to "What does Holden mean when he says the last 2 sentences?". I've only just found out what Holden was getting at (hopefully.) I might not be able to say this in English class and get away with it being a "correct" answer, due to how specific one must be when answering questions, although it is worth a shot.

Don't ever tell anybody anything. If you do, you start missing everybody.

It could probably mean Holden likely refers to him missing everyone because of how emotionally dependent he has become towards the people he came close to establishing a relationship with. He's had an emotional breakdown as a result. However, one must not forget that Holden's 2 brothers have basically been "lost." Allie died from Leukemia, which accounted for much of his changes, speaking psychologically. To top it off, D.B. is just another Hollywood sell-out because he writes for personal income and not for the joy of it. Therefor, he feels very distant from D.B.. Another example would be Jane Gallagher, the girl who Holden has a crush on. He misses her, even though all he has to do is call her. However, due to his inability to get close to someone, he just can't. He enters the state of isolation and segregation because he does not feel comfortable sharing his feelings with anybody. He runs away from the possibility of establishing a relationship by implying "if you do not get close to anyone, then you will avoid much trouble; you will be safe."

Of course, this could just be me rambling on, but that's pretty much how I interpreted the ending for the book.