Is introversion/extroversion just a set of beliefs?

Extroverts are people who get energized being around other people, and introverts get energized being by themselves. Common knowledge states that you are just born somewhere on this spectrum and that’s just the way you “naturally” are.

I’ve heard Brooke mention briefly that extroversion/introversion just come from thoughts, and I wanted to clarify this.

So are we all actually in full control over how extroverted and introverted we are?

Is the feeling of getting “energy” — either from being around others, or alone — just coming from a set of beliefs that then create the feeling of “energized”? According to the model (which is always working), I would have to say “yes”, which would then negate the common belief that you can’t help being either way.

So technically, someone who has identified their whole life as an introvert and has up until now believed that they get their energy from being alone, could (if they so chose to) turn themselves into a very extroverted person just by changing their beliefs?

And if so… does this imply that while we may have “in born” personalty traits that have developed from either nature or nurture… absolutely none of that is set in stone and a solid part of who we are? Do we really have the power to completely redesign the person we are in any way we desire?