Okay, entropy, here's one approach.
You notice that every time you are in situation A, you do act Z. And it irritates you.
You notice this again and again.
You ask yourself: Why do I keep doing Z?
You ask yourself: I keep doing Z when I am in situation A. What is the connection between these two events?
You ask yourself: When I am in situation A/ do act Z, how do I feel? What is the consequence of doing act Z? Supposing instead of Z, next time I am in situation A, I try act P? What might happen? Might I feel different? Might others react differently to me?
Then you have a few failed attempts at trying Act P. And you get pissed off with yourself, but what you fail to realise is that these failures are the beginning of something new.
Eventually you strike gold. You found yourself in Situation A, tried Act P and got a completely different outcome. Result! You have learned something about yourself, about life, and you are now in a position to (wait for it...wait for it...)
(...here it comes...)
change yourself!
'Tis possible. I have done it a hundred times over and will continue to do so until I draw my last breath.
FWIW even if you don't try and change yourself, life will alter your personality without you realising it. Now, are you happy to subject yourself to other forces in this way? Wouldn't you rather excercise some control over that?
Pick one thing about yourself that you find irritating. Nothing too overwhelming, just a minor to medium fault. I have no doubt that with dedication you can change it - it might take days, weeks or months. But depending on how much application you give it, you can change it.