Tell a child, a husband or an employee that he is stupid or dumb at a certain thing, that he has no gift for it, and that he is doing it all wrong and you have destroyed almost every incentive to try to improve. But use the opposite technique, be liberal with encouragement; make the thing seem easy to do, let the other person know that you have faith in his ability to do it, that he has an undeveloped flair for it - and he will practice until the dawn comes in at the window in order to excel.
Dale CarnegieWhen dealing with people, let us remember that we are not dealing with creatures of logic. We are dealing with creatures of emotion, creatures bristling with prejudices and motivated by pride and vanity. ...Any fool can criticize, condemn, and complain - and most fools do. But it takes character and self-control to be understanding and forgiving.
Dale Carnegie