Adam Smith Retrospective IFrom Part III, Chapter 2, of The Theory of Moral Sentiments, whose first edition Adam Smith published in 1759 . . .
He is a bold surgeon, they say, whose hand does not tremble when he performs an operation upon his own person; and he is often equally bold who does not hesitate to pull off the mysterious veil of self-delusion, which covers from his view the deformities of his own conduct. Rather than see our own behaviour under so disagreeable an aspect, we too often, foolishly and weakly, endeavour to exasperate anew those unjust passions which had formerly misled us; we endeavour by artifice to awaken our old hatreds, and irritate afresh our almost forgotten resentments: we even exert ourselves for this miserable purpose, and thus persevere in injustice, merely because we once were unjust, and because we are ashamed and afraid to see that we were so.
So partial are the views of mankind with regard to the propriety of their own conduct, both at the time of action and after it; and so difficult is it for them to view it in the light in which any indifferent spectator would consider it. But if it was by a peculiar faculty, such as the moral sense is supposed to be, that they judged of their own conduct, if they were endued with a particular power of perception, which distinguished the beauty or deformity of passions and affections; as their own passions would be more immediately exposed to the view of this faculty, it would judge with more accuracy concerning them, than concerning those of other men, of which it had only a more distant prospect.
This self-deceit, this fatal weakness of mankind, is the source of half the disorders of human life. If we saw ourselves in the light in which others see us, or in which they would see us if they knew all, a reformation would generally be unavoidable.
See also "Preach What Your Practice."