I believe it has nothing to do with who you actually are, but how you feel and see yourself in the situation. That means you perceive the other person or circumstance as a threat.
If you were to ask Charles Darwin the difference between a human and an animal, he’d probably reply, “Not much.” Observe yourself and you will notice a variety of animal instincts. One of them is a switch to aggressive behavior when you feel threatened.
I haven’t engaged in any academic research on this topic; my understanding comes from observation. Look at dogs. Most often you’ll find the biggest and strongest are gentler than the smaller ones. Observe other animals. Generally, the bigger they are, the gentler their behavior. Of course there are exceptions – crocodiles and lions are always ready to kill – but that’s their nature. They’re predators and they hunt to survive.
Now look at managers. The ones at the very top in a company, or outstanding leaders in their fields, most the time are very gentle humans – Type B personalities. On the other hand, there are those climbing the ladder of success and often do not realize there is an end to the ladder. These are the Type A personalities! (Unfortunately, I have to count myself in that group.)
When a person is in harmony with their environment, they have no reason to be aggressive. But as soon as things become unbalanced, physical and mental problems arise. As soon as an individual feels threatened, the tendency is to revert to the animal mode of behavior, which is absolutely normal. You could take the most balanced, easy-going, individual, but attack them from behind, and he or she might turn around, take a stick, and hit you right over the head.
Self-defense is a natural instinct in all of us. Many things can trigger it. For example:
Let’s assume you’re driving your car down a narrow street on a rainy day. A car approaches you from the opposite direction and you realize there is little room to pass. You slow down and edge as far to the side of the street as you can.
The other driver does not slow down or move over. He continues moving right at you, flashing his lights. As he gets closer to you, he blasts his horn and drives through a big puddle sending water over your windshield and momentarily impairing your vision. I bet you will feel the urge to aggressively respond, even if you are normally the calmest of drivers.
The older I become, the more I observe myself. I know I am often very aggressive (I laugh and say it comes from birth, because I was born in Basel, Switzerland). But to tell you the truth, it’s just because I feel threatened, either at a conscious or unconscious level.
Now, be honest with yourself. Does it happen to you, too? If it does, use every bit of your self-knowledge and understanding to retain your balance. It’s not easy, but it’s better for the well being of those around you, and for your own health!