Have you ever been in love with somebody who was already taken? Married or just has a boyfriend or girlfriend? How did you cope up with that feeling? Have you tried to be a third party? Or you just simply ignore that feeling? Or you decided to stop seeing the person hoping that the feelings will fade?
In this world full of temptation, it's hard to control one's self. Specially for some guys, it's hard for themselves to control being attracted with other woman. But it still depends on one's capability of self control. There are people who can remain loyal and honest with their loved ones and try to stay away from any possible temptation that could go along their way. Specially in a long distance relationship.
Self control must be well practiced and one must have it whether it be in this situation or any other case.