St. Isaac the Syrian

If you cannot be merciful, at least speak as though you are a sinner. If you are not a peacemaker, at least do not be a troublemaker. If you cannot be assiduous, at least in your thought be like a sluggard. If you are not victorious, do not exalt yourself over the vanquished. If you cannot close the mouth of a man who disparages his companion, at least refrain from joining him in this.