Hello BMR,
Time for a confession.
I have an overactive imagination, and when I RP I like to get into my character's head and in effect "become" him for a while. I think what he thinks, feel what he feels, experience what he experiences... I do not just read the posts, I live them! Not 100% of course, but close enough to make a difference.
So when my writing partner, or the GM, manages to hit my buttons -- oh man, what a rush!
But on the other hand, a negative scene can affect me just as strongly, and even worse, it can "bleed through" into RL. This is, for example, why I am reluctant to play out non-con scenes. It's not that I cannot write a rape scene, I think that I can, but for the next day or so I will have very wrong thoughts and may be an unpleasant person to be around (so I delegate the disturbing stuff to secondary characters or create NPCs).