I "went out" with a girl while she was on a break from her boyfriend (I was the reason they were on a break). Through semantics and smoke and mirrors she wasn't "cheating," but it never felt right and I never felt comfortable about it. I wasn't surprised when she went back to him, but it sure as fuck hurt. Still does.

I've learned a bit from the experience, although I'm sure there will be more to learn once the smoke clears.