Anger is an unpleasant emotion usually directed at someone or something perceived as having done us undeserved harm. It is not an accidental injury which outrages us as much as intentional harm, or thoughtless negligence.
Unresolved anger can lead to resentment and/or depression. Someone feeling angry will usually have a lack of joy, a lack of judgement, a sense of inbred hate, and overall frustration.
Anger as a sin
In Christian tradition, anger is one of the Seven Deadly Sins (the word wrath is often used to refer to it in this context). Uniquely among the seven deadly sins, anger was at times exhibited by Jesus - for example, when He turned the money lenders out of the Temple in Jerusalem. Since Jesus was without sin, it follows that not every instance of anger is sinful: anger on behalf of a righteous cause is permissible, and can even be desirable. On the other hand, anger for selfish or worldly reasons is a step on the path to damnation; famous examples of sinful anger include Henry II's ordering of the murder of Thomas a Beckett, and King David's murder of Uriah the Hittite in the Book of Samuel.
Unfortunately, the young mental health field has relied almost exclusively upon the expression of anger as the primary mechanism for dealing with this powerful emotion. While expression is important at times, when solely relied on for relief from anger, it has limited value because mere words or behaviors cannot make up for the depth of resentment and bitterness that has been denied in significant relationships in childhood and adolescence. Many health professionals believe that while men feel anger more intensely than women, women are more likely to hold long-term grudges.
Anger also can lead to poor physical health.