From the text:
Then he came back and sat down with the paper in his hand. "Oddly enough, this wasn't written by a practicing poet. It was written by a psychoanalyst named Wilhelm Stekel. Here's what he--Are you still with me?"
"Yes, sure I am."
"Here's what he said: 'The mark of the immature man is that he wants to die nobly for a cause, while the mark of the mature man is that he wants to live humbly for one.'"
Catcher in the Rye