“Pray without ceasing” (1 Thessalonians 5:17 ). Pay strict attention to your heart and watch over it, so that it does not give admittance to thoughts that are evil or in any way vain and useless. Without interruption, whether asleep or awake, eating, drinking, or in company, let your heart inwardly and mentally at times be meditating on the psalms, at other times be repeating the prayer, ‘Lord Jesus Christ, Son of God, have mercy upon me.’ And when you chant, make sure that your mouth is not saying one thing while your mind is thinking about another.
~A Discourse on Abba Philimon
Prayerful Life 