Character Flaw

Everyone has flaws in their character. It is what makes them an individual.  I am sure that I have lots a few but I know the highest reigning one...

Once someone annoys me, makes me angry, or just overall doesn't care what is going on in my life and only really cares about their own, I have a really hard time having patience with them.  I forgive, always. I feel like that is a great part of my character, but forgetting is something completely different. It takes me a really long time, or a good all-out screaming match discussion. 

Its just amazing to me, for example, I get mad at a friend if we go out to dinner, and they talk only about what is going on in their life, with never one question about how I am, or what I have been up to. I don't want the conversation directed to me at all times, but if it is not going back and forth, then it is not a conversation, it is a lecture.  (P.S. I never want to be the person that only talks about myself, so if I do that to you, feel free to throw your drink at me). Once that happens either over and over again, or in conjuction with something else, I have a really hard time getting over it. 

Obviously this is an overexaggeration, but it made me laugh.
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 This is something that I really want to work on.  I don't want to automatically be annoyed by everything someone does just because I am annoyed by one thing. But how do you fix that? How can you tell yourself, I will not be annoyed?