You two have likely found that you're at odds in the way you think, communicate and approach life in general. You're just such different people, with personality traits that seem to be in conflict. You naturally possess a more forceful, dominant personality than your partner, and could find their more introverted or cautious approach to life to be a hindrance to your naturally high energy.
They could feel overwhelmed by your seemingly aggressive communication style, and might respond by retreating into a protective shell that cuts off any possibility for understanding. It's likely that you're both more attuned to the differences between you than the similarities, and to the qualities you don't like in one another rather than the qualities you respect or appreciate. This is simply a natural, if unfortunate, focus for you two. But this relationship between you could also have an overall positive effect -- it forces you to examine your own natures and make conscious changes in the ways you meet the world. For example, you, who are the more dominant partner, could learn that your style of communication really is sometimes too harsh or aggressive for more sensitive types, and could learn to tone it down; and your more reserved partner could learn to broaden their mind and assert their personality in a more positive way.