Maybe I'm a bit too optimistic in believing that as a society, we're way beyond the tired and outdated misconception that personality type could ever be accurately assumed merely from one's disposition in social settings. Besides, there's plenty of theorists that claim there is no true introvert or extrovert, only a wide spectrum of ambiversion.
Regardless, I'll clear up their definitions by reiterating what you've probably already heard a million times before: your label is only derived from the source of your energy. Sure, the way you satisfy this social need may manifest in stereotypical behaviors for some, like loquaciousness or timidity for extraversion and introversion, respectively—they just aren't necessarily determinants of these extremes.
For instance, and a good number of friends can confirm, I talk quite a bit (in certain settings). I can't exactly designate this as a more extroverted quality of mine, for the nature in which I open up and contribute really doesn't depend on the size of the group I'm with or who is even in it. These factors certainly play a part in my comfortability with talking in general; but just because I'm comfortable doesn't mean I'm always leading conversation (and yeah, I have just as much trouble understanding as I do articulate it).
But it's still safe to say I've found myself to be an introvert after being given a fresh slate at college, in a different place with different people under different circumstances.
Trying to live in the same way I had prior to this was practically impossible.
I started from scratch—practically relearning myself all over again.
Once I began to separate the concept of personality type from my most obvious social tendencies, I had an easier time realizing that after expending a solid amount of conversational topics and mental energy, I had to take at least double the amount of time to recharge. Granting myself this sort of self-care has been absolutely essential in maintaining the same sort of personality I often used to claim as an extrovert's. It has nothing to do with the way I present myself; rather, it's all about what happens behind-the-scenes.
And perhaps I even misidentified myself to an extent before. I mean, I still interact with people in the same way I used to, I now just need to pace myself a bit more in order to function just as well as I used to in social contexts.
In fact, besides my roommates (who probably take note of the amount of time I contently spend on my own), I speculate that hardly anyone else has any idea that I've undergone this change. It's subtle. And as I've grown older to a point of matured self-awareness, the steps necessary to fulfill my most basic emotional needs have ingrained themselves pretty naturally in my routine.
And so, it's important to consider the possibility that none of this is polar after all. We are so ridiculously complex in the ways we are made that it's actually kind of silly to categorize ourselves in such a way that seems to give permission to make judgments of others a little too quickly.
Each person's true self is going to look vastly different than your own—the only thing that matters are the conditions in which you are most comfortable revealing it.