In Psalms: The Prayer Book of the Bible, Dietrich Bonhoeffer writes:
"But it is a dangerous error, surely very widespread among Christians, to think that the heart can pray by itself. For then we confuse wishes, hopes, sighs, laments, rejoicings--all of which the heart can do by itself--with prayer. And we confuse earth and heaven, man and God. Prayer does not mean simply to pour out one's heart. It means rather to find the way to God and to speak with him, whether the heart is full or empty. No man can do that by himself. For that he needs Jesus Christ" (pp. 9-10).