[watwut]

Because most people are somewhere in the middle in almost any way you define it. Most people need both time with other people and time alone. Most get tired when being with people all the time and their mental health goes down when being isolated.

Whether you derive energy from other people or whether they are draining is also dependent a lot on who those other people are and whether you have have social skills currently (e.g. how much effort it takes to you to figure out what to say).