In social psychology, internal justification is a way of resolving cognitive dissonance which underlies the most powerful kind of attitude change. E.g. 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 work in an awful job internally. You would in fact be persuading yourself.
Definition