The Other Woman and Man

What makes you guys do it? I'm sure we've all be attracted to someone who is in a relationship and we've probably all been at least hit on by someone who was in a relationship. What made you guys take that last step and become involved with the person? Did you feel bad about what you were doing? I'd also be interested in hearing from people who have cheated. I'm no angel, I met this guy who I was insanely attracted to and I talked to him on the phone and via email for two years but I only ever met him once when my ex and I had broken up for a week and I honestly wouldn't have even met him then if I hadn't been on a break from my relationship. Still, I couldn't go through with the betrayal. Thanks for your answers.