Unfulfilled expectations can lead to anger. What are your expectations of yourself and others for this situation? Are you expecting more than is realistic for this person in this particular situation?
Examine your underlying expectations about what you need to be happy and live the type of life you want. Examine your expectations from others. Perhaps you have higher (or different) standards than others. Perhaps you expect others to follow them as well as yourself. You may even be right. But these are your expectations of others–not theirs. They are who they are, and one root of anger is not accepting people (or events) as they are.
“Entitlement thinking” and high expectations about what we should receive cause a feeling of being “in a hole.” They cause some people to see themselves as victims and view the world negatively. These expectations are the cause of a deep sense of powerlessness and prolonged resentment about being treated “unfairly.” The deepest source of many people’s anger comes from when some important value or goal is threatened and they feel that they are losing control of the situation. They may not want to admit feeling hurt or fear. (Some may think such an admission is a sign of weakness.) Yet these are the underlying feelings that will help to identify which values and goals are being threatened.
The real threat may not be the surface issue (being late to the movie) as much as the underlying issue (not being important to someone you love or being mistreated). Identifying emotions of fear and hurt will open the door to these underlying issues. Once you get in touch with the fear and hurt, what images, thoughts, and underlying issues are associated with [cause] them?