i got drunk and i slept with my friends fiance and i

i got drunk and i slept with my friends fiance and i didnt feel bad about it because she did the same thing to him. however i do feel bad on some level because it is not the way my mother raised me they have since gotten back together, and are doing well, but he is still cheating on her, but not with me.... i dont deserve forgiveness, but i wish to be excempt of some of the guilt i have.