"How have I misunderstood about being angry at other people? "
I'm just angry in general so yes it can sometimes be directed at other people. On Saturday, for example, I felt car sick on what should have been a very straight forward journey. I was angry about that, but it wasn't directed at anyone.
"She's very angry with things that are just part of normal life. Having to work full time, flat being too small, people on the bus. Really she's disappointed in how her life has turned out and knows she has no one to blame but herself. It's a pretty common feeling!"
No, that's not me. That sounds like a dissatisfaction with her life in general. Mine is more that someone will say something that I disagree with, I will then disagree, then they react and it escalates, kind of thing. Then because I've had an argument, this will be replayed in my head for a while.
I mentioned elsewhere that I'm pretty happy with my life in general - I like my job at the moment, for example.
On Saturday, I did get grumpy about every single thing in the shops, but had no such problem yesterday so I think some of it is biological i.e. how I feel in myself, lack of sleep, stomach troubles, etc.