[Gustavus Adolphus]

This can usually be avoided if your friend would have just asked ahead of time if it's cool with you, but maybe he didn't think he had to because he introduced you to her or something. I don't know, I don't see this happen all that often since I got out of the office environment.

When it comes to shorter term relationships that don't work out, the best line I've ever heard that gets me to snap out of it if thoughts like yours ever start creeping in is this:

"She was never yours, it was just your turn."