Any observer of human emotions recognizes that certain circumstances and actions by others seem to make us mad. We were frustrated, i.e. prevented from achieving some desired goal.
Some theorists believe that anger just naturally results from frustration.
This is called the frustration-aggression hypothesis. There are several physiological reactions that accompany frustration, including higher blood pressure, sweating, and greater energy. Psychosomatic symptoms, such as heart disease, occur more often in people who are cynics and distrustful but hold in their anger. Some of us explode, others swallow feelings. Our blood pressure sometimes goes up more when we explode, at other times it goes up more when we swallow the feelings, depending on the situation.