Buddha says: The cause of suffering is desire. One aspect of desire is attachment to impermanent things; another is the pleasure-seeking will of the body; both are Ego – the false self, which acts out of fear of loss, with limited vision of the Absolute and impeded access to the Greater Wisdom. As one becomes self-aware, discipline will become necessary in order to act from Source, from Wisdom, in doing right, regardless of immediate pleasures and desires. Discipline is the triumph of wisdom over desire. The Warrior stops himself from doing what he wants to do after recognizing, however subtly, that the doing is not acting from Source, but rather from Ego. He knows that, ultimately, action from Source brings greater pleasure and long-term peace; immediate pleasures are nothing in comparison to the promise of ultimate serenity.
This is why we must use any means necessary to become aware of ego and fear-based desires, and to act instead from Source and Wisdom. Self-Discipline is one of the first significant steps along the path of the Warrior.