Introverts (or those of us with introverted tendencies) tend to recharge by spending time alone. They lose energy from being around people for long periods of time, particularly large crowds. Extroverts, on the other hand, gain energy from other people.
I had no idea I am an introvert, I thought because I am out going and can meet random people easily, that I was an extrovert, much to my surprise I am not.
I get exhausted by being around others, and prefer and need much time alone to recharge