One Must Establish in Oneself the Thought of One’s Own Sinfulness
Labor to generate and establish in yourself the thought of your utter worthlessness and sinfulness, which stir up God’s wrath against you. And when you come to prayer, do not appear before the face of God in any other way than as such a… sinful, utterly worthless creature under God’s wrath. As soon as you receive this sense of your condition, you will not be able to refrain from crying out: “O Lord, save me, O Lord, help me speedily!”
Why does prayer go poorly? Because the need for God is not felt. “Well, we can manage all affairs and needs ourselves, right?” Pray so that God grants you such feelings. Without them you will perish.
(Letter 967. Vol. 6, p. 81)