If I had my counselor's hat on, which I do, I'd say:
1) Make sure that the person you love knows how damaging cheating is to a relationship by having them read a book by one of the top relationship researchers/experts like Sue Johnson or John Gottman (there are many harmful relationship books out there to avoid).
You and your partner must have realistic expectations about how and why a long term relationship works and learn about the basic relationship maintenance skills that keep one going.
2) Cheating happens when a partner dosen't know how and why healthy relationships work or because they have core-relationship needs that are not being met. Learning how to hear and meet their needs may be indicated.
3) If the person is someone you really love, attend 7 or so, sessions of evidence-based couples counseling (EFT Couples Counseling is the best in the world).
As with my book recommendation above, don't waist your time with couples counseling that is not supported by strong empirical evidence. It's like the difference between taking an FDA tested medication and one that is not tested.
There's always an exception to the rule here. If you know of a relationship counselor or pastoral counselor etc who has really worked effectively with couples, you may consider working with them as well.
A properly trained couples counselor will have the knowledge, skills and experience, to either help you repair the relationship in as few as 5-7 sessions or identify problems and provide/support and alternative strategies best suited to the problem.