"Will God, if I ask, forgive me these things by which I am pained and by whose memory I am tormented, things by which, though I abhor them, I go on backsliding? Yet after they have taken place the pain the give me is even greater than that of a scorpion’s sting. Though I abhor them, I am still in the middle of them, and when I repent of them with suffering I wretchedly return to them again."
This is how many God-fearing people think, people who foster virtue and are pricked with the suffering of compunction, who mourn over their sin; yet human prosperity compels them to bear with the backsliding which results from it. They live between sin and repentance all the time. Let us not be in doubt, O fellow humanity, concerning the hope of our salvation, seeing that the One who bore sufferings for our sakes is very concerned about our salvation; God’s mercifulness is far more extensive than we can conceive, God’s grace is greater than what we ask for.
St Isaac of Nineveh
Isn't this spirit, this experience of the enormity of God's grace, what underlies the Jesus Prayer? And it is only in opening oneself to that immeasurable grace that we are in turn filled with mercy and compassion for all of creation - as St Isaac himself says elsewhere:
What is a merciful heart? It is a heart on fire for the whole of creation, for humanity, for the birds, for the animals, for demons, and for all that exists. By the recollection of them the eyes of a merciful person pour forth tears in abundance. By the strong and vehement mercy that grips such a person’s heart, and by such great compassion, the heart is humbled and one cannot bear to hear or to see any injury or slight sorrow in any in creation. For this reason, such a person offers up tearful prayers continually even for irrational beasts, for the enemies of the truth, and for those who harm her or him, that they be protected and receive mercy. And in like manner such a person prays for the family of reptiles because of the great compassion that burns without measure in a heart that is in the likeness of God.
How can we think we know how to pray in the face of that calling, or how, should I say, can we doubt that the only real prayer of such a heart must be, "Lord Jesus Christ, Son of God, have mercy on me [and through my prayers on all of creation] a sinner"?