We must look for a master who is not himself in error: his lessons will show us when we go astray to right or left and our excess in the matter of attention…If you can find no one, pray to God in contrition of heart and with tears, appeal to him in your nakedness and do what I shall tell you.
You know that we breathe our breath in and out, only because of our heart…So, as I have said, sit down, recollect your mind, draw it-I am speaking of your mind-in your nostrils; that is the path the breath takes to reach the heart. Drive it, force it to go down to your heart with the air you are breathing in. When it is there, you will see the joy that follows: you will have nothing to regret. As a man who has been away from home for a long time cannot restrain his joy at seeing his wife and children again, so the spirit overflows with joy and unspeakable delights when it is united again to the soul…
Next you must know that as long as your spirit abides there, you must not remain silent nor idle. Have no other occupation or meditation than the cry of: “Lord Jesus Christ, Son of God, have mercy on me!” Under no circumstances give yourself any rest. This practice protects your spirit from wandering and makes it impregnable and inaccessible to the suggestions of the enemy and lifts it up every day in love and desire for God.
But if, in spite of all your efforts, brother, you do not succeed in entering your heart as I have directed, do what I tell you and with God’s help you will achieve your end. You know that man’s reason has its seat in the breast. In fact it is in our breast that though our lips are silent, we speak, make decisions, compose prayers and psalms, etc… After putting all thoughts away from this rational power (it can be done; you need only to will it), present to it the prayer, “Lord Jesus Christ have mercy on me,” and force it to utter these words interiorly, excluding all other thoughts. When in time you will have mastered this practice, it will undoubtedly open for you the entrance to the heart”. (PG 147, 961-966; cf. Writings from the Philokalia, pp. 32-34).