This is an extremely powerful quote that describes the guilt that Amir feels about his past. He realizes that he himself has grown to be a different man and judging someone based on their past rather than their current personality is incorrect.
In the novel, Amir comes from a wealthy family and carries the characteristic of selfishness and greed early on. On the other end, Hassan never possessed many things, allowing him to be more grateful for the little amount he had.
Pin This pin or quote eventually turns into Amir overcoming his guilt. Amir comes back to Afghanistan and saves Hassans son and gets his butt whooped which helps him overcome his guilt of never being a good friend to Hassan.