Wikipedia
Self-monitoring is a theory that deals with the phenomena of expressive controls. Human beings generally differ in substantial ways in their abilities and desires to engage in expressive controls (see dramaturgy). Self-monitoring is defined as a personality trait that refers to an ability to regulate behavior to accommodate social situations. People concerned with their expressive self-presentation (see impression management) tend to closely monitor their audience in order to ensure appropriate or desired public appearances. Self-monitors try to understand how individuals and groups will perceive their actions. Some personality types commonly act spontaneously and others are more apt to purposely control and consciously adjust their behavior.
People who closely monitor themselves are categorized as high self-monitors and often behave in a manner that is highly responsive to social cues and their situational context. High self-monitors can be thought of as social pragmatists who project images in an attempt to impress others and receive positive feedback. Conversely, low self-monitors do not participate, to the same degree, in expressive control and do not share similar concern for situational appropriateness. Low self-monitors tend to exhibit expressive controls congruent with their own internal states; i.e. beliefs, attitudes, and dispositions regardless of social circumstance. Low self-monitors are often less observant of social context and consider expressing a self-presentation dissimilar from their internal states as a falsehood and undesirable. People who are unwilling to self-monitor and adjust their behavior accordingly are often aggressive, uncompromising, and insistent with others. This may make them more prone to condemnation, rejection, and the possible consequent feelings of anger, anxiety, guilt, low self-concept, isolation, and depression. Even the occasional indiscretion can make social situations very awkward, and could result in the loss of a friend, co-worker, client, or even job. Those who are willing to adjust their behavior will often find that others are more receptive, pleasant, and benevolent towards them.