It's like saying you can rape proof yourself. You can't be responsible for your spouse's actions. Period.
I'm of the belief that the only reason a person allows themselves to cheat, is because they wanted to and their character was of such to do so.
We've all had past issues, dramas, heartache, family problems, and crap that wasn't perfect in our childhood. As adults, we know right from wrong. I don't want to know WHY they did it. I already know. And it wasn't because we didn't affair proof "us". It's because they allowed themselves to.