After any confrontation, whether verbal or physical, it is natural for the mind to switch from the "fight or flight" response to "rest and recover" mode.
Prompting reflections of how to prevent similar future occurrences, the mind naturally recreates past scenarios and resolutions on how it could have resulted better. In the case of violence, the quest for self preservation births a systematic form of combat.
As early civilizations formed, wars amongst clans and kingdoms over resources became one of the dominant reasons for conflict, creating new systems of combat involving primitive tools such as swords and shields. In order to have an organized fighting method, combat systems were standardized so that armies could function efficiently.
This gave rise to competing supremacy of combat systems; martial arts.