"I have to be alone very often. I'd be quite happy if I spent from Saturday night until Monday morning alone in my apartment. That's how I refuel."
[edit] to clarify to whom I'm agreeing.
No psychologist worth their salt would define an introvert that way.
http://www.dictionary.com/browse/introvert says:
"introvert
noun
1. a shy person.
2. Psychology. a person characterized by concern primarily with his or her own thoughts and feelings (opposed to extrovert ). "
(edit: added "don't")
"I have to be alone very often. I'd be quite happy if I spent from Saturday night until Monday morning alone in my apartment. That's how I refuel."