Well, it's sort of like this. When you're in a relationship with a girl that you actually have feelings for, and you cheat on her with some hot chick with tigobitties for a fantastic fuck, that makes your original girlfriend feel like dirt, feeling she isn't worth anything to you. I mean, there is a margin of error where it may be acceptable if you tell your girlfriend that you're dating someone to make them feel better and boost self confidence, they might understand, but that defeats the purpose of CHEATING.