There are those of whom I speak and who are called heretics by me. They are the ones who say that in our present age there is no one in our midst who is able to observe the commandments and be like the holy fathers….Those who declare this is impossible have fallen not into one particular heresy but into all of them, so to speak – a heresy surpassing all others in its impiety and greatest blasphemy. They are buried underneath it….The one who speaks in such a manner turns all of Scripture upside down….These antichrists affirm, “It is impossible, impossible.” How then is it impossible? Tell me. In what other way did the saints shine on earth and did they become lamps of the world? If it were impossible, they would never have succeeded in it. For they were men like us, and possessed no more than we do except a will directed toward the good. They had zeal, patience, humility, and love for God. Therefore, acquire all this and your soul which today is as hard as rock shall become a fountain of tears inside you. However, if you refuse to suffer such anguish and affliction, at least do not say that all this is impossible.
—St. Symeon the New Theologian. Discourse XXIX: “The Heresy of Pusillanimity”