On the Burning of the Heart Toward the Lord
If your heart grows warm at the reading of your usual prayers, then by this method kindle the warmth of your heart toward God. The Jesus Prayer, if you perform it mechanically, gives nothing, like any other prayer spoken by the tongue alone.
Try, during the Jesus Prayer, to think more vividly that the Lord Himself is near, stands before your soul, and listens to what happens in it. Awaken in your soul a thirst for salvation and confidence that from no one but the Lord can we expect salvation. Then cry out to Him, mentally beholding Him before you: ‘Lord Jesus Christ, Son of God, have mercy on me, the sinner’ or: ‘Merciful Lord, save me by whatever means you know.’ The matter is not in the words at all, but in the feelings toward the Lord.
Spiritual burning of the heart toward the Lord is love for Him. It is kindled by the touch of the Lord to the heart. As He is all love (1Jn 4:8,16), the touch of Him to the heart at once kindles love for Him. And from this love comes the burning of the heart toward Him. This is what should be the object of your seeking. The performance of the Jesus Prayer is only an instrument for this, or rather, only the labor that shows the strong desire of the soul to find the Lord.
Let the Jesus Prayer be on your tongue, the foreseeing of the Lord before you in your mind, and a thirst for God, or communion with the Lord, in your heart. When all this is constant, then the Lord, seeing how you are striving, will grant what is asked.
Do arrange all this, take it as your guide, and read it more often so as to refresh in your memory how you ought to act.
(Letter 339. Issue 2, p. 208–209; Letter 1338. Issue 8, p. 93–94)