Understanding J.S. Mill's Utilitarianism, EP 7 The Ultimate Sanction

Once we understand the principle of utility, what are the motives for obeying it? Mill writes that this is a problem for all moral theories. The general question is "Why should I be moral?" The particular question is "Why should I promote the greatest happiness for the greatest number?" Is it because I want people to like me? Or because I am afraid they will dislike me?" And what role does a person's conscience play in making moral decisions? How does conscience attach itself to the principle of utility?