ID is the manifestation of an individual’s primal needs and desires. Should one’s inhibitions be thrown to the wind and action taken on purely selfish motivators their ID would be displayed prominently. Superego is essentially the opposite of the ID. Its purpose and function is to guide the individual within a set of moral guidelines. It would be the voice of reason that prevents people form acting on impulse only and provides restraint so that thoughtful decisions can be made before actions take place. Ego is the man in the middle so to speak. It is a moderator of sorts that creates a dialog between the other two in order to prevent them from cancelling one another out. The ego can be likened to a protocol that enables fulfillment without over indulgence. Defense mechanisms are the the gates between the three that basically keep the system in check. By doing so they prevent a runaway scenario that could cause the system to collapse and fail. Such failures would look like nervous breakdowns and delusions. I recall a time as a child when I accidentally killed my little duckling pet. I was total smitten with it and wanted it with me at all times. When I realized what I had done my defense mechanism was to deny it was dead and convince myself it was sleeping. The purpose of this was to prevent extreme emotional distress that my very young mind and heart could not bare. It did help me, but only for a brief time period. Quickly I had to admit to myself the reality of my situation and accept it.