If anger is unexpressed great problems can occur and create other problems as well.
Unexpressed anger can lead to pathological expressions of anger such as a personality that seems hostile and perpetually cynical and hostile. It can also lead to passive-aggressive behavior which is defined as getting back at people indirectly without telling them why rather than confronting them head-on. When one has not learned how to constructively express their anger they often criticize everything, make cynical comments and are constantly putting others down.
Due to the above actions, often people who are not constructively expressing their anger do not have successful relationships.
 

Summary of How to Deal with Unexpressed Anger:

In order to deal with anger, one must not only one’s inner responses yet they must also control their outward responses.
In order to this one must calm down inside and take steps to lower one’s heart rate in order to let the feelings subside.
As Dr. Spielberger reminds us, “When none of these techniques work, that is when someone or something is going to get hurt.”