You could start out on even ground, but over time it becomes apparent that you're polarized in how you live your lives. Your lover needs a lot of security within a romantic relationship, much more than you do. In fact, you need the opposite -- a lot of independence, freedom and space.
They have a hard time giving that to you; they might actually cling tighter the more you demand space, which causes a big rift between you. They start to seem controlling and rigid to you and you seem unreliable and unstable to them. It's not that these are fair or correct characterizations; it's just that that's the effect you have on each other, and those are the qualities that are exacerbated within each of you when you're together. When it starts to seem like either of you is not getting what you want, you naturally respond by insisting on it, instead of keeping a cool head and taking a more gentle approach to getting your way. The interesting thing is, you stand to learn a lot from each other -- if you can. There are aspects to each of your approaches that are valuable if combined with the strengths of your partner, and it's up to you to figure out, together, what those aspects are. Once you do, you stand a much better chance of blending your strengths and presenting a united front to the world.