"Why is sex viewed as one of the most important components of love?" I always wondered. The reason behind most of the problems in relationship, whether its breakup or an argument, is based upon sexual matters most of the time. In your case, I can understand its not you who committed the sin, but your thirst or want to have sex.The moment you saw Resha(the seducer) coming to kiss you,your mind must have gone blank.You couldn't think of anything else,your future, the possible guilt, your innocent GF, nothing at all.Thats how powerful sex can be. But,now instead of regreting over your past,I think it is wise to think about your future. First of all, if you keep it as a secret,I am sure your girlfriend will never find out(unless Resha blackmails you to have sex again like in movies, but don't do it).But it can be very hard to supress guilt while you are progressing on your relationship.I feel sorry for you. But if you think you can't, go ahead and confess it. Your acceptance could depend on how much she loves you.If she was always after you, she might forgive and accept you. Boy, you betrayed your love, therfore, you got to be ready to surrender and face any punishment. Just think, what would you do if she had done the same thing and she dared to confess infront of you? Would you accept or leave her?