God what a brilliantly comforting thread! I'm not the only hair-trigger-tempered interrupter out there! 
I talk too much, and interrupt, then worry that people think I'm a self-absorbed twat. I think I might come across as bit of a know-it-all, although I really don't mean to. 
My quick temper is the worst, particularly when I'm driving - I'm just absolutely fucking horrible...
'Come on you cock sucking fucknugget, what the fuck are you doing? Why would you stop here you TWAT?? Oh I see... it's a zebra crossing...'
At least the other person can't hear me, although I'm not averse to making my feelings plain on occasion. I don't do it when I've got DD in the car, though I'm still impatient. I'm trying hard to get a handle on it, and on my temper in general. I'm also impatient in pretty much every other way, too. I have to bite my tongue constantly not to express my exasperation with how incompetent everyone around me is, especially how SLOOOOOWLY they do things!
My temper ignites very quickly and easily, but usually cools down quickly too, after which I feel shit. DP calls it my anger-guilt-anger-guilt cycle.
In my defence, I'm quite a self aware person, and I do analyse why things have happened and apologise when I've been unreasonable. I just wish I wasn't so quick off the mark with my reactions.
I'm working on it intensively now, and I'm much better than I used to be.
I drink much too much, swear too much, sit on my lazy arse too much. I'm a complete pedant about grammar and spelling, and it does affect what I think of people. I appear really confident and sociable, but I can actually be incredibly antisocial and am a mess of neuroses and insecurities. 