The angry man

I draw usually when i'm bored. In family meetings, on the way home, at home... nearly every where. I don't plan to draw something, just start with few lines and suddenly an idea pops out. It's really a mystery to me that where does the idea come from? Why many of my drawings show an angry or sad man?

It's also interesting that how easily you can evoke a feeling by drawing few lines. How some do it better (beside the practice)?