Im naturally not a bitchy person, but when i hang around with certain people i find that every second word that comes out of my mouth is negative. Look at your friends and the people you hang around with on a daily basis, are they bitchy? do all they talk about is negative things about other people? I found this with a couple of people i was friendly with and so began to make an active attempt to steer the conversation onto something else. Not only did it stop me feeling like such a bitch, but i think it helped my friends in a way too.
Theres nothing more irritating than someone who slags someone off and then is their best friend to their face. It actually one of the only things that really get on my tits. Like lola stars said, quit acting like a bitch if you want to - its in your power, you just have to become more aware of what you are saying.
Before you bitch think - do i really mean what im saying, or am i just trying to add to the conversation? If you dont mean it, dont say it. If you do mean it, and are going to say it, think about if you would say it the person who you are talking about's face. If not, dont say it either.
As much as people flame others for being "bitches", it is innate in all of us, you just have to control it. Once you clear up the negativity you'll feel a lot more positive about yourself - which will help with the whole feeling angry thing.
Sorry that this reads like a counsellor rant, but you know what i mean.