Stressed out!
What is stress all about? Of course, I do not have all the answers, but a famous psychiatrist named Alfred Adler, an early associate of Sigmund Freud, strongly believed that personality difficulties are rooted in a feeling of inferiority that derive from restrictions on an individual's need for self-assertion.
Let me put this in simple terms: sometimes you need to blow your top.
Do you ever think about some of your replies to an aggressive statement? Do you ever wonder what would have happened if you had expressed your real feelings? Do you ever lay in bed and think about what happened during the day and how you could have handled it better?
Tension builds from frustration. If what I asked above applies, think about risking someone's anger. Read more about this in Gigenrenzer's 'Thinking Rationality in teh Real World".