"How to deal with that?"
If you can't control someone else then why worry about it? Either don't get married, or accept the possibility of cheating. Or don't sign any contracts and live in a state where cohabitation does not equal marriage. You seem young, if it's humanly possible, try to make it to your thirties without committing to a woman, and you will likely reap the rewards that come with experience like cynicism, getting used to being free and being set in your ways, and an established career. Or you can get married young have a kid or two, make your exit plan early, then you don't have to worry what marriage is like because you already experienced it. Then you can be single for a decade or two, and then get married again when you are older and wiser if that is what you want.
If you can't control someone else then why worry about it? Either don't get married, or accept the possibility of cheating. Or don't sign any contracts and live in a state where cohabitation does not equal marriage. You seem young, if it's humanly possible, try to make it to your thirties without committing to a woman, and you will likely reap the rewards that come with experience like cynicism, getting used to being free and being set in your ways, and an established career. Or you can get married young have a kid or two, make your exit plan early, then you don't have to worry what marriage is like because you already experienced it. Then you can be single for a decade or two, and then get married again when you are older and wiser if that is what you want.