I've never cheated on any of my gfs, no matter how the opportunity was presented to me... If you aren't attached to her enough to be willing to forego other options, why start a relationship at all. If you were attached enough but aren't anymore, you should probably end it whether you've cheated or not. If you can honestly tell yourself, "If (other girl's name here) wanted to, I'd totally cheat," then there's something amiss... at least that's how I treat relationships... I guess it was different in high school. But high school was, in general, fairly retarded.