Anger is an important emotion in human relationships. It occurs when a person feels badly treated. It tends to give rise to blame, and sometimes to retribution. Since ancient times, it has been thought by many that anger is a wrong and mistaken emotion. Most commonly, however, as research using daily emotion diaries has shown, although an episode of anger can lead to violence, and can be an occasion for breaking off a relationship, more usually it can enable people to renegotiate an aspect of a relationship in which something has gone wrong. Angry outbursts are common in childhood, but their frequency declines with age. Some people, however, have a genetically influenced trait of being often and unreasonably angry. This trait is more common in males than females and is exacerbated by having been, in early life, the target of anger by parents. The trait becomes a risk, in adulthood, for criminality and addiction. Therapy programs can enable parents to be less angry with their children, and for members of couples to manage their anger. Over the centuries rates of homicide have declined as individual vengefulness has been replaced by justice administered by the state.