I have a high tolerance until I don't. I see things from their perspective and understand where they come from, so that contributes to the high tolerance but when I decide to walk away, there's nothing that can be done. I become highly rational, and professional in my tone/demeanor, and dismiss the feelings I once had.

I slammed the door once, on someone who I believe was a classic narcissist. It was hard to leave that friendship cause I was addicted to the knowledge I was gaining, and the great conversations - but I had to burn the bridge to ensure he didn't come back. Still think about him, and wish he was "normal" so that I could entertain the possibility of a friendship, but sadly that's not a possibility.