Emotional Intelligence is a key success factor in business and private life. As Software Engineers emotions are usually not your main focus in daily work. Our strengths are logic, algorithms, rational behavior and solving difficult puzzles.
But we have to work with others in teams, as users and customers. Mostly they have no technical background and come from complete different domains. This makes it difficult to interact with them in a proper way. One key in this definition is the separation between oneself and others. This leads to interpersonal intelligence (oneself) and intrapersonal intelligence (others) the perspective.
Wikipedia says: "Emotional intelligence (EI) is the ability to identify, assess, and control the emotions of oneself, of others, and of groups". 
Intrapersonal intelligence describes the ability to have positive relationships and/or good communication between people. This means that you understand what people fell and need.
The key competences of intrapersonal intelligence
- Sense of Self,
- Self-regulation and
- Personal Leadership.
Sense of Self
Your moods/emotions are always present and determine automatic reactions. One way to control these automatic reactions is self awareness. Unfortunately your brain has no direct access to your emotions (imagine these parts of your brain have not direct connection). The only way to get access to your current main emotions is your body.
- Recognize your own feelings, emotions and reactions.
- Develop mindfulness to get a better awareness.
Strong emotions hinder us to act in a conscious way. Quite often we fall back into automatic reactions. This is your heritage from the time we hunted mammoth and cave bears and in some situations not bad, but in daily business the automatic reaction may not the best way. Strong emotions produce inner states which lead to automatic reactions. One way to control these reactions is pause for a moment, slow down, start to think and react aware.
Sounds easy? But it's really hard to do. What you need is a deep understanding of your personal weak points, automatic reactions, and the ability to recognize your own feelings. You can recognize your own and others feeling with help of body language.
- Control your current inner state with self awareness.
- Bring your own automatic reactions to mind and interrupt if needed.
The long term goal is to build-up personal leadership. Improve the knowledge about your own emotions, automatic reactions, weak points and actions. This will help you to understand your personality in a better way. It is a long term process which may need years.
- Know and lead the parts of your personal personality.
- Care about your own strengths and weaknesses.
Interpersonal intelligence describes the introspective and self-reflective capacities. Know your self, your emotions and what your weaknesses and strengths are, being able to control your own reactions.
The key competences of interpersonal intelligence are:
- Reduction of Automatic Reciprocal Effects and
- Creating Relationships.
Is the ability to notice the emotions of others and to interpret them in a correct way. If you know what the currently dominant emotions of other are, you may react properly and express empathy.
Contact statements help to create better contact to your peers and may bring the dialog to a meta level. These statement should always be phrased as questions (you may be wrong with your interpretation). E.g. 'Surprised?', 'Disagree?" or "Skeptical, em?"
- Try to recognize the feelings and emotions of others and peers.
- Express sympathy and understanding in an appropriate way.
Reduction of Automatic Reciprocal Effects
Personality styles are different from person to person. They manifest with automatic reactions (weak points). Typical styles are resistance, meritocratic, expressive, dominant, vulnerable, independent, introverted or adapting behavior.
If somebody is in the resistance style and you increase the force/efforts, you will create more and more resistance. What you can learn from martial arts (judo, kung-fu, jiu jitsu, etc.) is that in some cases just doing the opposite of the expected reaction brings success.
- Bring automatic reactions with others to your mind (interrupt if needed)
As long term goal you should create positive relations. The foundation to archive this, is an open attitude and the will to take time. Good relationships need time to grow. The better you understand your own and others emotions the successful you may be.
- Create positive mid- and long-term relations with others (this needs investment)