In social psychology, this is a way of resolving cognitive dissonance and underlies the most powerful kind of attitude change. For example, if you feel, on reflection, that you have an awful job, you can resolve (psychologically) the dissonance between the cognitions 'I am a sensible person' and 'I choose to work in an awful job' either externally or internally. An external justification might be 'I do it for the money', but that wouldn't change your opinion of the job. However, if you began to consider the job in a different light and saw its more positive aspects you would be justifying your decision to stay in an awful job internally. You would in fact be persuading yourself, the most powerful way of changing anyone's attitudes.