Emotions can be undesired either to the individual experiencing them, but also can be undesired to the other persons, groups of persons, organizations, sub-cultures, and civilizations such as Western civilization, which can be viewed as the emotion being subjected to the individual's or someone else's discouraging meta-emotion about the undesired emotion or can be even repressed by the meta-emotions. Thus one of the most distinctive, and perhaps challenging, facts about human beings is this potential for entanglement, or possibly opposition, between emotion, meta-emotion, will, and reason.
Some state that there is no empirical support for any generalization suggesting the antithesis between reason and emotion: indeed, anger or fear can often be thought of as a systematic response to observed facts. In any case, it is clear that the relation between logic and argument and emotion is one which merits careful study.
Emotion as the subject of scientific research has multiple dimensions: behavioral, physiological, subjective, and cognitive. Sloman argues that many emotions are side-effects of the operations of complex mechanisms (e.g. 'alarm' mechanisms) required in animals or machines with multiple motives and limited capacities and resources for coping with a changing and unpredictable world, just as 'thrashing' can sometimes occur as a side-effect of scheduling and memory management mechanisms required in a computer operating system for purposes other than producing thrashing. Such side effects are sometimes useful, but sometimes they are dysfunctional. Other theorists, often influenced by writings of Antonio Damasio argue that emotions themselves are necessary for any intelligent system (natural or artificial).
Psychiatrist William Glasser's theory of the human control system states that behavior is composed of four simultaneous components: deeds, ideas, emotions, and physiological states. He asserts that we choose the idea and deed and that the associated emotions and physiological states also occur but cannot be chosen independently. He calls his construct a total behavior to distinguish it from the common concept of behavior. He uses the verbs to describe what is commonly seen as emotion. For example, he uses 'to depress' to describe the total behavior commonly known as depression which, to him, includes depressing ideas, actions, emotions, and physiological states. Dr. Glasser also further asserts that internal choices (conscious or unconscious) cause emotions instead of external stimuli.
According to Damasio, feeling can be viewed as the subjective experience of an emotion that arises physiologically in the brain. 
Many psychologists adopt the ABC model, which defines emotions in terms of three fundamental attributes: A. physiological arousal, B. behavioral expression (e.g. facial expressions), and C. conscious experience, the subjective feeling of an emotion. All three attributes are necessary for a full fledged emotional event, though the intensity of each may vary greatly.
Robert Masters makes the following distinctions between affect, feeling and emotion: "As I define them, affect is an innately structured, non-cognitive evaluative sensation that may or may not register in consciousness; feeling is affect made conscious, possessing an evaluative capacity that is not only physiologically based, but that is often also psychologically (and sometimes relationally) oriented; and emotion is psychosocially constructed, dramatized feeling."
In pop culture there are sub-cultures which cultivate the expressions of anger and rebelliousness even when they are not really angry, its members encouraging each other to express the anger by internalizing meta-gladness about it. Encouragement (i.e. meta-gladness) and discouragement (i.e. psychological repression) of selected emotions - instead of mere awareness and equal interest in all emotions - can be considered as additional source of organizational climate, family dynamics, psychodynamics, personality traits, and of mental disorders, including depression among others.