Emotional intelligence, or EI, is the ability to understand and manage your own emotions, and those of the people around you. People with a high degree of emotional intelligence know what they're feeling, what their emotions mean, and how these emotions can affect other people.
 
For leaders, having emotional intelligence is essential for success. After all, who is more likely to succeed – a leader who shouts at his team when he's under stress, or a leader who stays in control, and calmly assesses the situation?
In the book Emotional Intelligence, author Daniel Goleman takes a comprehensive look at what emotions are and why we have them and how we can get better at managing them. He defines EI as the array of skills and characteristics that drive leadership performance.