The Desert Mermaid

This can also often be an Introvert/Extrovert thing. Extroverts do generally get pepped up by going out and doing something active, while Introverts need to be quiet and alone to recharge. I can't remember the author right now, but there's a book called "The Introvert Advantage" that really opened my eyes to a lot of this stuff, and helped me figure out some of the things that were triggering problems and some strategies for coping with them.