You have very different ways of thinking, which could lead to some basic misunderstandings of who you both truly are. Although you each entered the relationship with the best of intentions and expectations, you've found that your ideas about life in general -- what's interesting, what's important -- are pretty different. This could lead to misinterpreting one another's basic natures, as it's easier to project your own ideas onto the other person than it is to step outside your own point of view to try to see things from their unique perspective.
You don't necessarily argue over your opposing viewpoints; it's more likely that you each just overlook the other's true feelings or opinions. You two have found that your communication styles are very different; your lover may be much more talkative while you're more introverted, for example. These differences may pose a major problem between you, but it doesn't have to stay that way. If you both make a conscious effort to be positive, accepting and encouraging of one another's individuality, rather than rejecting the differences between you, you'll both feel much more willing and able to express yourselves in the way that is most natural to you. Acceptance is key here, in order to make this relationship work.