Last Two Sentences

What is meant by the last two sentences of the novel: "Don't ever tell anybody anything. If you do, you start missing everybody." 

The last sentences of the book show why he doesn't like to have deep emotional connections with people, and shows that he realizes he actually cared about some people. Holden Caulfield is afraid of becoming attached to people. This probably has to do with the traumatic experience of his brother Allie dying young. They had a really deep relationship, and it was taken from him, causing much damage. He shelters himself from repeating this experience by avoiding meaningful relationships altogether. This quote also shows that he is realizing he actually liked some people in his life. He rejected many people and alienated himself from everybody. He realizes that he was rejected by them, and that he should have been more appreciative. He doesn't want to leave them because he misses them. He is afraid of change and doesn't want to leave his old life. This final quote is a reflection on his behavior and experiences with meaningful relationships throughout his life.