Extroverts get their emotional energy from other people. Such as when other people get excited, they get excited as well. Introverts emotional energy comes from within so how other people feel doesn't really affect them. When the two meet, the extrovert essentially sucks the emotional energy out of the introvert leaving them tired and annoyed. As has been noted above, introverts need time alone to recharge while the extrovert needs people to recharge.

Then you have me. An introvert with some schizoid tendencies ... not only do I need alone time to recharge, but frankly I don't want to be around people at all anyway.