Is cheating part of reality in a relationship?

Is cheating part of reality in a relationship to a certain degree. I am 35 years old now and I am thinking about getting back in a relationship with a former flame. When I met her she was with a abusive boyfriend but later I found out that boyfriend was really her husband he is a foreigner so maybe she married him for visa reasons... As much as I like her I can say I knew that the boyfriend existed but when I found out that it was her husband it put a certain bitter taste in my mouth it sort of turned it into a mega lie in my opinion but then I get real with myself and I realize that I myself have cheated in fact 75% of the people that I know have cheated in a relationship or on their wives is cheating just a reality?

Is cheating a relationship test in away? Can cheating save a relationship? Or maybe just cheating is something that is a phase in our lives when I was in my teens I really believed in love and could be faithful to one woman but in my 20s it was impossible but now in my 30s I look back at my 20s and just see it as a phase. I think this woman could make me really happy and maybe she did just marry him to help him with the visa but it put a bad taste in my mouth should I just look back on that and say that she was young just as I was and forgive it or should I look at it at it more closely and tell myself once a cheater always a cheater?