"Be Yourself"

I try to hold on to the belief that people can change. I think it would be so unnatural to think that any one person is doomed (if this is the appropriate adjective to use) to be just one way all his/her life. Besides, isn't there that saying "the only thing that is constant is change." I also believe that it can be good to reassess and to change those things about yourself that aren't good or constructive. This is really hard to do though. There is that other saying 'be yourself', and sometimes I feel like the effort to change those things about yourself you don't like is going against being oneself.
For example, I have always been a transparent person. Ask anyone who knows me well. They can tell you that I can't lie to save my life, neither can I keep my emotions or thoughts hidden for very long. My face is like a polygraph machine. One wrong twitch and you can tell a falsehood from fact. This has been a blessing and a curse. A blessing because my friends know that I always tell them the truth, I call it as I see it, and what they see is what they get- literally. It's been a curse in that I can never seem to mask what I am thinking or feeling when I need to be poker-faced. It's a good thing I can't stand gambling because I would be flat out broke ten times over by now.
Lately though I have found that this transparency has just been the source of arguments. See, I am not an extrovert by any means. Often times I am not comfortable with people I don't know. I do like going out and socializing but sometimes I can't find the energy needed to get to know strangers better or to be excessively spunky when out. I like being calm and listening to people tell their stories, if these people are people I see at parties and events but not necessarily people I choose to spend my weekends with. I don't necessarily think this is a bad thing since, if I am with close friends, I am usually more than happy to gab away as well. I suppose I should be more sociable but, again, I am the first to admit that my people skills are not that great. This becomes even worse when I am irritated or pissed off or angry about something. When I am pissed or angry this emotion tends to overwhelm everything else. My husband knows that the worst way to surprise me with a gift is to make me angry that he forgot the event first. This is the way I am. Plus, this anger often needs to be expressed and recognized for it to die. And the sooner, the better, because festering anger is just plain ugly.
So, imagine me pissed off about something, not being able to say anything about it, and then headed off to socialize with people who are friends but not my close, close friends. A disaster waiting to happen right? Well, I've been told that I have to change this aspect of myself-letting my emotions (namely anger and/or irritation) show when out with people. It gives the wrong impression and just makes me unpleasant to be around. I know this. And believe me I have tried to change it. This is what I do now: I picture things I like, I think of topics I can discuss with the people there- topics I know something about and are totally unrelated to the reason for my irritation, and then I get some kind of dish or drink that I can munch on in between conversations. Sounds like a plan? I thought so until I tested it last night.
My hubby and I were supposed to meet some people for dinner and a free gift certificate after work. On the way to the meeting place, my hubby says "let's reschedule because Peter has been texting to meet up and is getting upset that I can't join again. I've canceled other times." Dilemma: do I insist on going and look like the bad guy again (introverted as I am) or do I just go along with it? So I say ok. Already I feel the irritation creeping up the back of my neck. Oh, I forgot to mention that we were having a pretty deep discussion about the household help just minutes before the topic change. I think to myself 'maybe I should just go home' but then I don't want to be labeled anti-social either. I am also after all trying to make an effort to be sociable. I know, I say to myself, I will try out the plan to divert my irritation. It should be ok. We go and meet up with his friends. The whole time I am thinking, ok, it's working. I can successfully keep my irritation at bay. I can socialize without it showing on my face. And then we go home. I am exhausted from the effort only to argue with my husband after about how I looked grouchy the whole night, and how his friends noticed and asked if I was angry, and how I just don't make an effort to change this. Naturally, this angers me. How can it be said that I am not making an effort when it took (for me) a lot of energy to think happy thoughts and to not let the irritation take over. And to have it categorically stated that there was not even one iota of change or effort was hurtful and insulting to me.
So I was left thinking, how much of oneself can we really change? It should be possible to change those things you recognize as needing improvement right? So why isn't it working for me when I am willing and trying to make it so?