Catechism of the Catholic Church
2732 The most common yet most hidden temptation is our lack of faith. It expresses itself less by declared incredulity than by our actual preferences. When we begin to pray, a thousand labors or cares thought to be urgent vie for priority; once again, it is the moment of truth for the heart: what is its real love? Sometimes we turn to the Lord as a last resort, but do we really believe he is? Sometimes we enlist the Lord as an ally, but our heart remains presumptuous. In each case, our lack of faith reveals that we do not yet share in the disposition of a humble heart: "Apart from me, you can do nothing." 20
2733 Another temptation, to which presumption opens the gate, is acedia. The spiritual writers understand by this a form of depression due to lax ascetical practice, decreasing vigilance, carelessness of heart. "The spirit indeed is willing, but the flesh is weak." 21 The greater the height, the harder the fall. Painful as discouragement is, it is the reverse of presumption. The humble are not surprised by their distress; it leads them to trust more, to hold fast in constancy.
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.