First you need to establish the definition of cheating, is it only physical or also emotional?
Would cheating be having a physical intimate moment with another person apart from you OR does it also include have a physical intimate moment with you but thinking of someone else during it?
Either way, it's not okay, yet when you truly love a person you talk things out and give him/her another chance.. You yourself aren't perfect and mistakes are there to be made and learned from in my opinion. And if, like I said, you truly love your partner, you'll show him/her that and be the bigger person.