Even if your partner doesn't start out being overly traditional in their values regarding commitment, duty and so on, they could become more so in this relationship, because of your rebellious insistence on independence. You could start out on even ground, but over time it becomes apparent that they need a lot more security within the relationship than you do. The bad news is, their natural response may be to cling tighter and tighter, which only causes you to run even more determinedly in the opposite direction.
The gulf between you widens as your perceptions of each other solidify -- they take on the role as the controlling, overly needy or demanding partner, while you're the rebellious and unreliable one who can't be counted on. Neither of these characterizations are exactly fair; it's just that you bring out these qualities in each other, because you're both naturally looking out for yourselves and your own interests in the relationship. When it starts to seem like you're not getting what you want, you naturally respond by insisting on it, instead of taking a softer approach. The blending of your strengths and seemingly opposing qualities has a much better effect. It might be that all your struggles over this subject lead to a forced compromise -- but it also could just be an ever-widening rift between you. It's up to you which of those possibilities comes true.