Xmas party, held at an external location. After some drinks, a co-worker whom I was friends with started flirting up one of the waitresses. Now, he was tall, well-trained, and quite attractive for women. It was just that he also was married and had a child.

I quietly sought out that waitress and told her about that, asking her to turn him down because nothing good would come out of that. She appreciated it and stayed out of his way.

Felt kind of back-stabbing him, but at the same time, also saving his ass from himself.