Happiness is attained when all of an individual's potentiality for a full rational life is realized to the utmost and the individual fully expresses all of her varied capacities. This striving for self-realization is the essence of being human. It can mean virtues, excellence, goodness or perfection. Moral virtues are achieved by means of a consistent practice that creates a habit of action. The principal ingredient in this process is the following of the mean between extremes.
Extremes are to be regarded as vices.
An action is not morally virtuous simply because it conforms with or is controlled by, reason. Insofar as that action conforms with or is controlled by reason it will automatically involve a mean between extremes. The Golden Mean is relative to the situation at hand and the person involved. For example, in times of war we should expect courage to lean more toward the side of excess for the soldier and more toward defect for citizens. The good is that which a thing aims to achieve in accord with it's inherent nature.