We don't choose to be annoyed, but we allow ourselves to be. Being annoyed never has a logical reason to it; it's an emotion; so by reminding myself of that I can make sure it doesn't negatively affect me. (Not that emotions are bad, but this one seems to only negatively affect me, so I don't want it.)

For example, when someone insults you in an offensive way. Why be annoyed? If it's true you should fix it; if it's false then he's mistaken. By remembering that, when I see that I'm about to become annoyed, my list reminds me to stay mellow.