We can all Introvert or Extrovert when required. Often, however, we can do the most, best or most enjoyable work when we are using our preferences, rather than our non-preferences. Being E or I does not mean that we extravert or introvert all the time - it simply means that we probably spend more time extraverting than introverting (or vice-versa). Even an extravert needs time to be alone, and an introvert needs interaction with people. But Is usually need more time alone, and vice-versa for Es.

Bad Joke: Judge: "What evidence does your client have to support his claim that he is an extravert?" Lawyer: "His wife will testify that when he has been fishing all day alone, and not got a single bite... he'll admit it openly, your honour".