Chronically angry people develop what's called "negative neuroplasticity." What it is, is the negative person has trained their brain to respond negatively (in anger) to everything happening in their life. They think, feel, and react in anger (sometimes paranoid rage) to everything, no matter what it is. Generally, people like this overreact a lot, are easily triggered into anger, have major trust issues, and are suspicious of everyone (which they have a hard time admitting to their relationship partner).

Also, people with anger issues are extremely charming and manipulative. Calm on the surface until an explosion of anger erupts, and then they go into silent treatment mode to punish the target of their anger. I know this, because the last significant relationship I had was with a guy who loved to use the silent treatment with me whenever he was angry at me; as a way to emotionally abuse and manipulate me.

Brain science is interesting in what it can reveal about why people think and act the way that they do.

It sounds like your boyfriend needs some help controlling his anger. And, I hate to say this, but it's very naive of you to think that your boyfriend's anger will never escalate to the point where he won't physically harm you.

You need to evaluate this relationship, to see if it brings you any benefits emotionally and psychologically. Living with someone who has chronic anger problems, is akin to walking on eggshells constantly because anger issues, left unchecked, are a form of abuse. That may be hard for you to accept and digest. But anger issues are tied to deeper psychological problems in the person.