While Jung is famous for saying no one is a pure introvert or pure extrovert, I will go beyond this to say there is no such thing as an introvert (or an extrovert). Most of us have a healthy mix of both introvert and extrovert tendencies with one set predominating overall or in particular circumstances, such as how we are at work. Even for those of us farther out on the continuum, where introversion predominates in a much more pervasive way, there is still no such thing as an introvert.
Thing implies noun. Introverts and extroverts alike are not nouns but verbs. Humans are always in a process of becoming; our thingness is an illusion.
There is a dilemma when considering personality in the context of the Buddha's teachings. On the one hand, we can observe predictable patterns of cognition, affect, and behavior (i.e., personality). On the other hand, there is no independent existence to these patterns. They are conditioned, for certain. Part of this conditioning is genetic, part is learned, and the remainder is constructed out of memory, expectation, and identification.
There is a dialectic between a skillful understanding of personal patterns and the desire to transcend these patterns because they do not lead to satisfying existence. Identification marks the key difference in these options. The goal is observe our personality tendencies without identifying with them. That is, we can recognize introverted patterns without making them the basis of our worth, identity, or personhood.
There is a plethora of introvert books that valorize the benefits of being an introvert. I've written one of them myself! However, this "pride of ownership" can go too far and will keep us from experiencing the deeper benefits that the Buddha's teachings have to offer.
The aforementioned dialectic represents a delicate dance between existence and essence, between process and becoming. The predictability of certain patterns can be useful as long as I keep my hands off of them. In other words, as long as I don't "own" the patterns, I can be informed by them without being bound by them.
I am an introvert. I prefer to spend time in solitude, get drained by certain types of social engagements, and have a tendency to process internally more than I speak. I am also not an introvert. I am no one. I am a collection of energies that transform moment-by-moment and the only way to be an introvert is to abstract myself from this flow through concepts, language, and memory. When I abstract, I remove myself from the lived experience of now and enter the world of imagination.
Imagination is fine as long as I know that is where I am at. However, we tend to mistake imagination for reality.
Knowing the patterns that make up our personality can be a useful shortcut for working through the affect of any given moment. The pattern can become a reliable cue to let go of an identification that is giving rise to discomfort, dissatisfaction, or distress. Beyond this cueing function, there is not much of value in the pattern.
This is a radical statement and one that contrasts with the valorizing of the introvert personality. I believe it is important for introverts to recognize their strengths and engage in good self-care. However, all beings—introverts and extroverts alike—will have to move beyond the label of self, personality, and story if they wish to taste awakening. Ultimately, we must relinquish personality.