How we handle stressful situations can make the difference between being assertive versus reactive, and poised versus frazzled. When under pressure, the most important thing to keep in mind is to keep our cool. 

Emotional Intelligence (EQ or EI) can be defined as

... so they don't overwhelm you and affect your judgment. 

• When you feel angry and upset with someone, take a deep breath and count slowly to ten. In most circumstances, by the time you reach ten, you'll figure out a better way of communicating the issue.
• Try to put yourself in the difficult individual’s shoes, even for just a ...

Sharing intimate feelings with someone in an appropriate relationship, in a manner that's nourishing and constructive, and being able to respond affirmatively when the other person does the same.

One method to consider when needing to express difficult emotions is the XYZ technique - I feel X when you do Y in situation Z.