"Lord Jesus Christ, Son of God, have mercy on me!!!" If one with desire and ceaselessly as the breath from his nostrils forms this Prayer, soon there will be in him the Holy Trinity, Father,
Son, and Holy Spirit, and make a dwelling in him, and prayer will devour the heart and the heart prayer, and a man will begin day and night to
perform this prayer and will be delivered from all the nets of the enemy. One should say the Prayer of Jesus in this way: "Lord Jesus Christ, Son of God, have mercy on me!!!"
Whether you are standing, whether you are sitting, whether you are eating, whether you are travelling, whether you are doing anything else, constantly say this Prayer, fervently compelling yourself, for it strikes the invisible enemies as a soldier with a strong spear. Imprint it on your thoughts, and
do not be disturbed or hesitate to perform it secretly even in the places of natural need. And when the tongue and lips grow faint, then pray with the mind alone. From prayer which is performed for a long time by the tongue there
proceeds prayer of the mind, and from that of the mind, that of the heart.
When the mind grows faint from constant concentration and the heart grows pained, then one may relax and sing a little.
St. Paisius Velichkovsky