The Myers-Briggs personality test is a fun one that everyone takes for something at one point in their life or another. It'll tell you who you are in four letters — either (I)ntroverted or (E)xtroverted, I(N)tuitive or (S)ensing, (T)hinking or (F)eeling, and (J)udging or (P)erceiving. These do mean different things than the words themselves mean - for example, judging is not exactly just 'you judge things', it's got more to do with organizational abilities and scheduling. For the majority of my life I've been a pretty devout ISTJ, or the 'robot' of the personality types. The three letters that fit the best with 'J', the ISTJ is a robot of a person, ultra-effective, ultra-unfeeling, you will bury those feelings and do what needs to be done.
But then I started thinking a little bit more, mostly about the introversion thing, because I started to realize that, while I am cripplingly shy, hanging around a lot of people gives me a buzz that being alone for several hours does not. I prefer being around people, even if I can't exactly talk to them - I'll take my computer and do homework in the library or in a lounge rather than holed up in my dorm room, for example, and the passing of people is something that's a lot better for me and my productivity than staring at a Kurt Cobain calendar while trying to figure out how to write the next part of whatever essay next is.
And then I started thinking about the other letters in my personality type, because while I am one of those ultra-organized people, always getting things done because I have my list and I will stick to it, the other things... started to stop fitting. And then I re-took the test with all of these new things in mind and surprise, now an ENFJ. Almost the exact opposite of what I thought before, complete with a heavy preference of 'Feeling' over 'Thinking.' Which is, honestly, taken my interests, is a little bit more fitting than 'the robot.'
But the reason this happened, the reason I locked myself in the little ISTJ box for nineteen years, is most likely because of how powerful that 'J' was. Because the organizational part of my personality is a giant part of my personality. It's a giant part of how I look at and interact with the world around me. And it took over, ushering away people, ushering away what was inside of me, ushering away feelings until it was the perfect environment for the organizational mind to fester in. It didn't help, probably, that I went to a small school, where I liked nobody, so I made zero effort to ever really make close friends, and the crippling shyness that sort of effects everything all the time, it all helped the 'J' take over literally everything until, finally, I was able to break out of that box.
It does show that, no matter how solidly we may think ourselves something — Hogwarts houses is another one, though I don't think I'm willing to give up Slytherin yet - we change. We accept what is fundamentally ourself more, or we reject it, pushing it to the side and out of the acceptable box of what we can be and what we can do, and then we have a two-in-the-morning panic about, "Oh god, I am not who I thought I was." And that's alright, because when you're so set solidly in your ways, there's no opportunity for opportunity. Sure, you can go forward on your predetermined path and strike it out there and maybe be successful in whatever you wanted to be successful in in your life, but those rambunctious decisions, those things that might not correspond with your plan, those are kind of lost to the wayside. And while just doing whatever you want forever is not a great thing, you do have to be realistic about it, being suspectible to change is something that's not a bad idea.