pretend you hit your head extremely hard at night. if you are hit in the temple area you bleed A LOT, so you could either:
A. Cut yourself there with something (this is what WWE wrestlers do to 'fake' blood, they cut their temple, and if you do it right it will bleed a lot and wont scar)
B. be boned
I can even vouch for the bleeding a lot thing from personal experience. In elementary school I hit a girl in the head with a small rock (yes I was a dumbass) and she bled so much. It was disgusting, but she was totally fine the next day.