As to concentration, there are times when prayer vibrates with joy and eagerness, and there are times when the brain seems stupider than ever, the imagination wanders far away and the feelings are cold and the will very weak. At such times it may be the best course simply to repeat acts of wanting God, of wanting to pray, of wanting to love, of wanting to have faith, not shriking from the repetition of the phrases and to ask him to use our little fragments of wanting and loving beyond what we ask or have. If the enthusiasm of a full heart brings us near to God, no less near to him is the prayer of a frail and sincere wanting. It may open the soul to a new pouring in of the love of God.
Not as a remedy for distraction but as a glorious prayer in its own right is the prayer known as the Jesus Prayer, used and love by Christians for many years and lately loved increasingly by many Christians in the West. The prayer is the repetition again and again of the words "Lord Jesus Christ, Son of the Living God, have mercy on me, a sinner." The repetition, many times and many times, is found to quieten the distracting parts of our personalities and to keep us wonderfully subdued and concentrated, and as we repeat the words again and again we bring into our hear the many people and needs about whom we really want to pray. As the words proceed the heart has the people on it one by one. To intercede need not mean to address phrases to God about this person or that, but to bear them upon the heart in God's presence.
Be Still and Know p. 60.