I guess it depends on your circumstances. If you're married with kids, I suppose it's harder to just sling him out the door. In that situation, I'd think really hard about whether the marriage is repairable. If you believe it was a one-off occasion and he is genuinely filled with remorse, maybe things will get back to normal eventually.
If you're just going out with the guy, my instinct would be to cut my losses. For me it's all about trust and respect. If I can't trust him, am I ever going to be comfortable with him going out with his friends without me? I also wonder how a guy who has any respect for the relationship and love for me would be willing to take those kinds of risks?
It's a toughie, but you know more than anyone if things can ever be good again.
I think you need to find out why that person cheated in the first place to see whether or not the problems can be fixed. It's not about whether you can forgive, but can you forget and trust them again?
Some men cheat because they are unhappy and some men cheat because they can. I'm with LindaCee - if you don't have children then it really doesn't matter why he did it, you get one life and you deserve someone who has more respect for you than this. If you do have children then you need to know why he did it - and that will help you decide whether it is likely to happen again. If he is truly sorry he will go into relationship counselling with you and he will take it seriously for the sake of your children. If he won't go - then you have your anwser.
I went through the same situation.. The truth is, if you really fo love him, the image of him with someone other than you will always be in the back of your mind, and i know it hurts. Things will never be the same because you can't just let something like go. Even if he never cheats on you again, it's already been done and you'll never forget it so you might as well stop wasting your time.
Like below says, depends on the circumstances. I always consider the time of how long the cheater has cheated, and if they told you, did you find out yourself or off another person. My ex was cheating on me, and I found out by myself because he was acting strange, not coming home for lunch and forever getting phone calls! He was cheating for a good few months. I knew I couldnt trust him from then. When he first cheated and beg for forgiveness, dropped at my feet, held on to my leg, cried and cried, I knew it was genuine guilt but when I found out the second time, he shed no tears, he just became defensive and nasty. He wasnt bothered what happen