Your body doesn't discriminate between dreams and waking reality. If someone says they're sorry in your sleep, your body may forgive them before your brain catches up. If you dream that they beat the royal hell out of you, and you wake up in the midst of said beating, your body will keep pumping adrenaline through your body until dream finally dissolves into daylight.
I've got the wrong guards up.
(Strangle by Sina Grace. Check out his blog to the right.)