‘Emotional Intelligence' is a metaphor that borrows from the notion of IQ. It implies that some people are better at handling emotions than others. It also hints that you might be able to increase your EQ. Practically, it offers a useful set of guidelines for doing just this. Emotional intelligence plays an integral role in defining character and determining both our individual and group destinies. It involves the ability to monitor one's own and others' emotions, to discriminate among them, and to use the information to guide one's thinking and actions. In short, to embrace the power of emotions intelligently. It involves abilities that may be categorized into five domains:

Self-awareness

Being emotionally self-aware means knowing how you feel in “real time.” Self-knowledge is the first step in being able to handle emotions. If you can see them and name them, then you at least then have a chance to do something about them.

Emotional literacy

Emotional literacy means being able to label emotions precisely. This includes the emotions of others and especially yourself. It also means being able to talk about emotions without getting overly emotional or (as happens with many people) denying them. Emotional literacy is not using ‘I feel...’ statements to offer opinions, ideas, etc. Thus 'I feel that is a good idea' is not emotional literacy, whist 'I feel angry' is.

Empathy & compassion

Empathy is the ability to feel and understand the emotions of others. If you can empathies, you can engender trust, as people desperately want to be understood at the emotional level. All great carers and nurturers major in empathy and compassion.
It also means appreciating and accepting differences between people, accepting that we have different priorities and capabilities around emotion.

Balance

The ability to balance emotion and reason in making decisions leads to good decisions. Emotion should not be abandoned, lest cold and callous decisions are made. Nor should logic be abandoned unless you want a wishy-washy outcome.

Responsibility

Emotional Intelligence means taking primary responsibility for your own emotions and happiness. You cannot say that others “made” you feel the way you feel. Although they may be instrumental, the responsibility is yours, just as if you kill someone, there is no argument that says that someone else made you do it.

So, emotions are one of the main things that derails communications and persuasions. Once people start getting upset at one another, rationalism goes out of the window. If you can identify and control your own emotions you have good chance of winning any argument. If you can sense the emotions of others, you have a chance to change them. And of course it all starts with yourself and your own emotions...