Anger is quite useless

Lately I've been losing my temper more than usual. I'm losing patience with people quickly and it's starting to worry me, because if I lose patience with people then they're going to lose patience with me. I don't need any unnecessary drama and don't want to start anything, but I feel dangerously large flickers of flame inside me during situations I would normally shrug off my shoulders. I'd like to blame it on the fact that I've been sick since last weekend but I also don't want to be disappointed when that turns out to be wrong. I don't know what's gotten into me lately. Today, one of my best friends dropped the ball on something she'd been promising me since last week - she promised that he would come to our study hall to help her with something tech related that she needed to do. She didn't tell me a specific day because she didn't want me to turn it into a big deal. I can see where she's coming from with that point because I definitely was making a big deal about it; I'll admit to that. I wasn't running around yelling about it or something like that, but I was visibly excited when we talked about it. I was even trying to figure out her plan about which day he was coming - not that she even formulated a plan - and I was nervous about what I was going to wear. That is all very ridiculous because he shouldn't mean anything to me but for some sick reason...I cared. It was not a big deal in the scheme of things, but to me it was. I don't know if she understood that when she decided not to message him and I didn't want to say anything. After all, I had a feeling this was coming; I should have told myself it would never happen in the first place so I wouldn't disappointed. But you know, when you're giddy, you don't think negatively like that.
When she first told me she wasn't going to message him, I was upset. Then I was upset that I was upset because I shouldn't be. Then I was mad. I was mad because this was stupidly important to me and even if she didn't feel like doing it...she had promised me. Gosh, I was mad for like an hour, and I blurted it out to someone because I couldn't sit there and not say something.
Then a joking around argument turned real for a second...
Then I got defensive over music...

This is worrying me.