Correcting mistaken thinking is the basis of some approaches to therapy. The idea simply put is that what we think controls what we feel. So the way to become happier healthier people is to change the ways of thinking that cause us problems and hold us back.
So the cognitive approach says if think that I am unworthy of love I will feel ashamed of who I am and this in turn will hinder my relating. The other way to look at it is that I feel ashamed of who I am and therefore I think I am unworthy of love which in turn hinders my relating.
In practice it is never as simple as taking a person who thinks he or she is stupid or unattractive and then convincing them otherwise.