A Voice from the Past - Gregory the Great

The ruler also ought to understand how commonly vices pass themselves off as virtues. For often niggardliness palliates itself under the name of frugality, and on the other hand prodigality hides itself under the appellation of liberality. Often inordinate laxity is believed to be loving-kindness, and unbridled wrath is accounted the virtue of spiritual zeal. Often precipitate action is taken for the efficacy of promptness, and tardiness for the deliberation of seriousness.

Gregory the Great, 540-604 AD, Pastoral Rule, Part I, Chapter IX, (The Nicene and Post-Nicene Fathers, Vol. XII, Philip Schaff and Henry Wace, translated by James Barmby, T & T Clark and  Wm. B. Eerdmans, 1997, p. 20)

How can we avoid trying to fool others and ourselves this way? How can we tell when it is happening?