Let’s say, your dearest friend needed a favor and you immediately promised him that you will do it. Days went by and you kept postponing it. Finally till the end you just didn’t do the job. Time comes, when you have to tell him that you are sorry. You are feeling miserable. That incident is eating you from inside. Finally to help yourself, you try to find out reasons. Certain reasons because of which you couldn’t do that job. Maybe because you had some important personal things to do. Maybe because it was not worth all the trouble. Maybe because he should learn to do his own stuff. In your mind, you know that you are being unreasonable. You know that you could have, and you should have done that job. It’s not your fault but, it is human nature to make up some comforting thoughts to ease our mental tensions Usually when our thoughts, attitude, beliefs all our in agreement with each other and things around us also support these thoughts then our mind is at peace and comfort. Cognitive dissonance is what can cause unrest in our minds. This is when our mental peace fails, and things seem in disorder and there is confusion in general. This is when the consistency theory kicks in. Our human mentality tries to find a comfortable situation to the ongoing problems. We try to achieve a balanced state which gives us some mental peace. This is called the Consistency theory.
We use four defense mechanism to keep our perceptions of the world consistent: stimulation, organization, interpretation & evaluation and memory.

1. Denial is when people are overwhelmed by the anxiety present within a situation, they can engage an even more severe form of memory repression. For example at school, a student seeing a grade of "C" next to their name, and automatically assuming the professor made a grading error.
2. In projection, anxiety is reduced by claiming another person actually has the unpleasant thoughts that you are thinking. You are attributing your own thoughts to someone else.