COME unto me, all ye that labour and are heavy laden, and I will give you rest.
Take my yoke upon you, and learn of me; for I am meek and lowly in heart: and ye shall find rest unto your souls.
For my yoke is easy, and my burden is light.
THE heart must gain rest with “Lord Jesus Christ have mercy on me”. The prayer refreshes, it does not weary.
(Source. I’ve corrected the English grammar a bit.)
Basil Pennington, fortunate enough to talk face-to-face with Elder Paisios about this, vividly remembered the counsel given to him (after an inauspicious beginning):
I QUESTIONED Father Paisios on his life: I don’t remember; I am an idiot.
Then on continual prayer: First you must find tranquillity and simplicity – to be free for prayer and know yourself; second, you must know the mercy of God; third, you must know that prayer is not a burden but a rest.
If you want to pray continually, you must be free from responsibility.
If you cannot be free, you must further the responsibility for others and you will share in the merit of their prayers.
From “The Monks of Mount Athos: A Western Monk’s Extraordinary Spiritual Journey” p. 52. My emphasis.
MY heart was troubled within me, and the horror of death fell upon me.
Fear and trembling came upon me, and darkness covered me.
And I said, Who shall give me wings like a dove’s, and I shall flee away, and be at rest?
Behold! I became an exile far away, and encamped in the wilderness. Pause. […]
BUT for my part, I cried out to God, and the Lord hearkened to me.
Evening, and morning, and at noon, I will declare, I will make known: and he shall hear my voice.
He shall redeem my soul in peace from them that draw nigh to me: for they were with me in great number.
God shall hear, and humble them, he that has existed from eternity.
Psalm 54 (55):4-8, 16-19 (LXX, my translation).