So this thing happened where my mood was effected by the mood of the protagonist in one of my stories. I sort of felt the same things I was describing--his decline into a depth of numbness like he'd never felt before. I don't think I was quite as far gone as him. But I saw an clear and obvious connection between my mood and my protagonist's mood.
So, ever noticed this happening to you? Sort of driv me crazy for a couple days. My character really wasn't feeling so hot.