If you have cheated on your significant other, and have any conscience, then you are likely shouldering substantial guilt. Taking steps to deal with what you're feeling, such as talking about it with someone, forgiving yourself and learning from the experience, is the only way to move past it. Without trying to cope, the guilt can easily eat away at you. It may already be having a negative affect on almost every aspect of your life, including your work and your relationships with friends.
Take responsibility for the guilt you're feeling. Trying to make an excuse for the cheating or being in denial about the guilt might only make it worse. Say the words out loud to yourself that you cheated, you feel guilty about it and that you're going to deal with it. Many times, saying the words out loud makes them seem more real than keeping them quiet and bottled up.
Consider confessing if you haven't done so already. If you haven't told your significant other that you cheated, that could be a major part of the guilt. Not only will confessing allow your partner to know the truth, but it could also allow some of that guilt to be gone knowing that he or she finally knows your secret.
Try to make it right for the other person. If your partner knows you cheated, you may feel guilty for not doing something to try to make it even a little better for the other person. If he or she hasn't already told you what to do to try to better the situation, then ask what you can do.
Evaluate and learn from what happened. It may help you to prevent it from making the same mistakes again in the future. Focus on what the actions were up until that point that got you in a bad situation and what you could have done differently. Also, think about why you allowed it to happen. When you figure out all the answers, it may help you to stop questioning yourself.
Talk to someone. Whether it's a religious leader, a therapist or a friend, talking about the reasons behind the cheating, as well as about the guilt your feeling, may help you get everything off your chest instead of keeping it bottled up inside. Knowing you have someone to talk to about it may also help you through the process of dealing with the guilt.
Start the process of forgiving yourself. Although your decisions showed supremely bad judgment, people aren't perfect and they mistakes. The act of bashing yourself on a daily basis and constantly feeling guilty isn't going to change the fact that you cheated nor is it going to make your partner feel any better.
In the back of your mind, always remember how guilty you feel and how your partner reacted and feels; it can help you avoid making the same bad choice again.