In Discourses, Epictetus explains this in true Stoic fashion:
“There are three things in which a man ought to exercise himself who would be wise and good. The first concerns the desires and the aversions, that a man may not fail to get what he desires, and that he may not fall into that which he does not desire. The second concerns the movements (toward) and the movements from an object, and generally in doing what a man ought to do, that he may act according to order, to reason, and not carelessly. The third thing concerns freedom from deception and rashness in judgement, and generally it concerns the assents.” (Discourses, III.2)
A thorough exploration of the Three Disciplines can be found in French scholar, Pierre Hadot’s The Inner Citadel (1998). Hadot explains in detail how all three disciplines are meant to help us live in harmony. According to Hadot the discipline of desire is living in harmony with the nature of the universe as a whole. This involves acceptance of our Fate as necessary and unavoidable, what Hadot calls Amor Fati, loving acceptance of one’s fate.