This comes from Donna Cunningham via Top Ten Sources (thank you Elsa!!):

Nothing makes us madder than some darned fool telling us the truth! If we grew up in dysfunctional families, in order to survive our upbringing, we learned to be highly sensitive, reactive, and always on the alert for a threat to the status quo. Thus, we tend to be easily wounded by even the gentlest reminder of the shortcomings of ourselves, our families, or other codependent ties. We may react with rage to even the most constructive of criticisms. In order to protect our denial, we may go so far as to sever relationships with people who are unwise enough to rock the boat with the facts. (No one said we were easy to live with!) . . .

Anger is the guard dog of denial. In some cases, the denial is so strong or the ego so vulnerable that anger is a pit bull. Do you resent people who puncture your illusions, threaten your denial about your own or loved one’s addictions or destructive behaviors, or make you face up to your shortcomings? Do you respond by closing down, running away, or cutting off the relationship? If so, you short-circuit your own growth and deny yourself real intimacy with others, an intimacy based on mutual honesty.

Anger keeps the past alive. [emphasis added] . . . In the course of our lives, we who come from dysfunctional families have had many causes for anger. Terrible things may have happened to us and to other family members because of our parents’ problems. As adults, because many of us didn’t know how to assert ourselves, we may play out the victim role. Our conditioned reaction patterns can leave a trail of broken relationships.

Anger may be all we have left to connect us to a family member, an old lover, or a former friend. By continuing to hold on to it, we keep the relationship alive and current, at least in our own minds. We make that person or incident very important in our lives and give them enormous power. We’d like to believe we’re still as important to them–not accepting that they may barely think of us at all any more.

The more energy we invest in the past in the form of anger, the less energy we have available for more intimacy and a better life today. It’s like putting a militia to work guarding a cemetery, when the same labor force could have built a new road.

Read more here. Many of us try to hide or suppress our anger, others hold onto anger for protection. This article states the issues very well, and offers tools for replacing anger with more constructive tools for protecting the Self.