Any man or woman who neglects to maintain inward vigilance, and only makes an outward show of holiness in dress, speech, and behavior, is a wretched creature. For they watch the doings of other people and criticize their faults, imagining themselves to be something when in reality they are nothing. In this way they deceive themselves. Be careful to avoid this, and devote yourself inwardly to His likeness by humility, charity, and other spiritual virtues. In this way you will be truly converted to God.
Walter Hilton