In the first section on the Creed, we dealt with the question of what we are to believe; in the sacraments section, how we are to worship Him. Now in this section on morality, we answer the fundamental question how are we to live?
Man has a natural desire for happiness, and happiness is the end (purpose) of all moral action. People do or do not do certain actions because they believe in doing so they will be happy. The desire for happiness is of divine origin in order to draw man to the only One who can fulfill this desire.
For Further Discussion: How Shall We Live? Happiness or Obligation; What is Virtue? Gifts and Fruit of the Spirit; The Moral Law