How do you know?

(St. Dorotheos of Gaza - found here)

“A man can know nothing about the judgments of God. He alone is the one who takes account of all and is able to judge the hearts of each one of us, as He alone is our Master. Truly it happens that a man may do a certain thing which seems to be wrong out of simplicity, and there may be something about it which makes more amends to God than your whole life; how are you going to sit in judgment and constrict your own soul? And should it happen that he has fallen away, how do you know how much and how well he fought; how much blood he sweated before he did it? Perhaps so little fault can be found in him that God can look on his action as if it were just, for God looks on his labor and all the struggle he had before he did it, and has pity on him. And do you know this, and what God has spared him for? Are you going to condemn him for this and ruin your own soul? And how do you know what tears he has shed about it before God? You may well know about the sin but do you not know about the repentance?”
~St. Dorotheos of Gaza