If I remember correctly, introverts get recharged from time spent alone and extroverts get energy from interacting with others. It's not actually as much about behavior as our innate nature and how we replenish our reserves, psychologically.

We can train ourselves to behave in any number of ways, but I'm not sure we can change our basic nature. And that's okay. We're not supposed to be like someone else. Otherwise, what's the point in being a unique human being in the first place?