One of my favorite stories from the Desert Fathers is about Father Apollo.

A young brother was greatly troubled by the demon of sexual sin and he went to an older man and declared his thoughts to him. When that old man, being inexperienced, heard the brother’s confession, he rebuked him harshly, saying he was unworthy of the monastery since he had entertained such thoughts. And when the young brother heard this, he despaired of himself, left his monastic cell and went back into the world.

But as the Lord would have it, Father Apollo ran into him. When he saw that the younger brother was upset and downhearted, he questioned him, “Child, what is the cause of your despair?” And the younger brother explained what had happened. When Father Apollo heard these things, he encouraged him, saying, “Don’t be surprised at these thoughts, child, and don’t give up hope for yourself. I, myself, even as old and gray-haired as I am, I am still very much bothered by these thoughts. Therefore, do not lose heart when you’re tested by a fire like this that isn’t healed so much by human effort as by God’s mercy.”

And the brother returned to his cell.

According to the Desert Fathers, some temptations cannot be healed by human effort but only by the mercy of God.