I've become an asshole

Tonight I was proofing a translation script that some new girl wrote. I have always hated proofing, because 90% of the scripts I've proofed just weren't up to snuff. They were missing crap, they were poorly translated, or they were poorly worded. So I wrote this girl a short critique on things she missed (she missed *a lot* of translations). And then I was told that she cried about it or something, and after an online discussion I suddenly realized it.

I've become a complete jerk. All this stress and fatigue must have changed me, because before I was always a super-nice guy (part of the reason why I become "just friends" with every girl I meet). But now it's like I have no tolerance at all. The slightest shred of incompetency is like lighting a 10-second fuse. This isn't just with translation, this is with everything lately. I've become angry enough to the point where sometimes I will hit things to relieve my anger. It is absolutely horrible that I've become this way. I hate the person I am right now, and I hate the fact that I've allowed myself to be worked hard enough to sink this low. I really need to take some time off and alleviate the pressure in my life before I destroy myself. Seriously.