For the desire of your heart is itself your prayer. And if the desire is constant, so is your prayer. The Apostle Paul had a purpose in saying: Pray without ceasing. Are we then ceaselessly to bend our knees, to lie prostrate, or to lift up our hands?....Even if we admit that we pray in this fashion, I do not believe that we can do so all the time.
Yet there is another, interior kind of prayer without ceasing, namely, the desire of the heart. Whatever else you may be doing, if you but fix your desire on God's Sabbath rest, your prayer will be ceaseless. Therefore, if you wish to pray without ceasing, do not cease to desire.
The constancy of your desire will itself be the ceaseless voice of your prayer. And that voice of your prayer will be silent only when your love ceases....Burning love is the outcry of the heart.
St. Augustine of Hippo, on Psalm 37