St Anthony the Great, text 41 from "On the Character of Men and on the Virtuous Life: One Hundred and Seventy Texts" in The Philokalia, vol. I:
Men of dull wits should not despair of themselves and become lazy, disdaining the life of virtue and of love for God as being unattainable and incomprehensible to them. They should, instead, exercise such powers as they possess and cultivate themselves. For even if they cannot attain the highest level in respect of virtue and salvation, they may, through practice and aspiration, become either better or at least nor worse, which is no small profit for the soul.