If you have never heard of the word amygdala, you're not alone, most people haven't. But it is an important term to be able to understand the overall aspects of your emotions.
The amygdala is a part of the brain's emotional system, and can cause us to resort to default behavior based on what we remember from prior, similar experiences. The amygdala basically exists to protect us when we become afraid, it is involved in the fight or flight response. It triggers an emotional response before the other parts of the brain are able to process what is happening.
The amygdala remembers frustrations, fears, hurt feelings, and anger from our past. The tension from these past experiences causes the amygdala to go into default behavior - meaning that we often feel before we think - which can create a potentially explosive situation. If you had a bad experience several years ago and are placed in a similar situation today, the amygdala will remember and trigger emotions that cause the body to respond. These feelings often cause us to react before critical thinking takes place - which happens in the rational part of the brain - and respond with angry words and/or actions.
The good news is that our brains have "plasticity", which means that they have the ability to grow new connections and pathways. As we practice using new strategies, increasing our emotional intelligence, we have the ability to kick these old behaviors and habits, and train our brains to respond differently in future situations.