"If your emotional abilities aren't in hand, if you don't have self-awareness, if you are not able to manage your distressing emotions, if you can't have empathy and have effective relationships, then no matter how smart you are, you are not going to get very far."
Being emotionally intelligent means that you can identify and manage not only your own emotions but the emotions of others too, it means you have awareness of your own feelings and are able to balance emotion and reason, you can recognize feelings and emotions in others and show empathy and compassion which is a crucial part of all relationships both personal and business.
There was one Harvard Business Review article I read a couple of years ago on how NOISE affects our decision-making skills. By noise they were referring to external influences, our emotional state, what mood we are in - these play a very significant role even in the most objective of decisions. People underestimate the influence of one's emotional state in any decision and when measured - people were shocked how results would vary drastically depending on their mood.
Hence having emotional competence to assess one's emotions or empathizing with others is highly critical and one should introspect in themselves if they feel to lack these instincts.
"Don't promise when you're happy, Don't reply when you're angry,
and don't decide when you're sad."