Hello folks. Found you guys (TRP) a while ago and I gotta say, you seem pretty awesome in what you can offer.

So I'm dealing with a little issue which I'm trying quite a bit to fix, but most books and whatnot tend to fail me (though I guess that's just moreso because I have issues finding a book towards such a scenario).

The issue is twofold: Insecurity and Aggression. I've never really felt sure or confident of myself and, at a young age, this made me quite a target for other children to push my around. Fast forward into highschool, the little crybaby became the school bully in an almost stereotypical fashion. Though I didn't actively go out and look for trouble, it was ridiculously easy to provoke me into picking folks up and pushing them into the garbage bin (the literal variant, might I add). As years go by, it was increasingly easy for me to anger. Every little thing someone said (and says, seeing how this is still current) really has an easy way of getting into my skin, internally making me feel absolutely abhorrent and self-deprecating and outwardly hostile and, if prodded enough, violent.

Post-School, I've grown pretty competitive, still aggressive, and can't help a certain need to claim dominance most given scenarios, even with things as mild as when little brother's began to walk ("Mine started walking before yours did! Hah!") or boasting inherent strength.

Seen as abrasive, borderline offensive, and even stupid to the public, how I act when alone or with a select few is harshly different, seeing as how I feel safer I suppose, though this is the way I've desired to. My temper is still short, given quite a bit of pent up anger, but I find myself much more quiet, more interested in reading and research into things that catch my interest, and I've even felt mildly annoyed that it came to a surprise to some that I possess an artistic penchant (seeing as how spend quite some time drawing and studying art books).

TL;DR: People believe I'm stupid and hostile because I have little control and a lot of pent up anger. How do I stop being easily provoked and be able to just be a grown ass man instead of being stuck as a highschool brute?

EDIT: I do apologize for going on a bit of a rant there, another fault is indeed lack of focus.