Perhaps the reason extroverts find interacting with people exhilarating is because it's not much work for them. Or perhaps because their perception of what is at stake in an interaction to be less than what introverts perceive. Better dancers step on fewer toes, as it were. And while I'm sure there are terrible dancers with a thousand hours on the dance floor, they must be a rarity.

Practice won't turn the introvert into the Haile Gebrselassie of social interaction (natural talent exists), but it will help. A couch potato will suffer through every mile of a run, until they give up. A seasoned runner will be energized by a run over the same distance.

I would characterize an extrovert's social interactions as existing in a state of flow. An extrovert has a perception of their ability that closely matches their actual ability. An introvert has too little confidence in their actual abilities, or too little ability.

So my point, and if nothing else, I've convinced myself of this fact, which might be useful in a fake-it-until-you-make-it fashion, is that social interaction is a skill, a learnable/teachable skill. And as such, we can group those who possess this skill into introverts and extroverts.