If you the spouse who has been wronged is able to forgive the one who committed the infidelity, then that is the first start. Some people say that once a spouse cheats and is forgiven, they will commit the act again. However this is just generalization. Some people are truly repentant when they realize they have made a very big mistake, and through seeing the error of their ways, realize that their marriage is the most important thing in the world to them. With the forgiveness and the repentance, the marriage is a good place to be saved.
Positive chances are only possible if both parties are willing to forgive each other with regards to the infidelity and want to work hard together to build trust and love in the relationship again. It's worthwhile to try and understand what lead to the infidelity and what can be done in the future to prevent it from happening. If efforts are made to address the needs of both partners in this vulnerable time, a strong and solid foundation for marriage can be built again.
Infidelity is a sign that someone isn’t fulfilled. That may not be due to the relationship itself, though, as very often a cheater might be in a good relationship and still not feel fulfilled. They might look outside the relationship for satisfaction, when really the solution lies within themselves. By talking with a marriage counselor, the couple can find out what that person felt like they were missing, or what they were getting out of the affair. Once that’s understood, both the individual and the couple can take steps to make sure both parties are getting what they need from the marriage.