Anger

I've been reading the HP series in anticipation for the upcoming movie. "Want to be up to snuff."
It seems that Snape is often angered. Made me think, I don't know that I really understand "angry", don't get me wrong, I'm sure I've been angry often. But I'm more likely to become frustrated and irritated. Not angry. I'll internalize a great deal when truly stressed. But angry, not often, then again, some of my more spectacular fights with my ex seemed closer to rage than anger.
When pushed to far or hard, I feel almost gleefully into rage. But so anger is a confusing emotion to me. Happiness, joy, sadness, and many aspects in between, are more easily understood; not anger.
And how can someone be angry all the time, is it more anguish that become aggressive? Or great, constant physical pain turned into aggressive actions toward other? Or simply a desired state of being? Something one has found to be their simplest form of a livelihood. I don't get anger, I've seen many facets(?) of it. Behaving spitefully, is this a form of anger? Being malicious?
I like to believe that I don't truly hate anyone. Hate being the polar opposite of love. You think about parents or sibs, you're spouse/partner, think of what they're doing, of what you'll be doing later in the day. That kind of constant effort is difficult, with regards to hating someone. It's easy to love someone, or many. However to hate anyone, that sort of constant vigilance, is tiresome. To think about something or someone all day everyday in a negative way, NO THANK YOU.
But so, back to my original point, maybe I don't understand anger, because I don't hate. (I try not to, anyway.