Though it might not be apparent until well into the relationship, you find that there are fundamental differences in your intellectual ideas that might create a real challenge to your connection. The ways in which your partner thinks about things turns out to be at odds with where you need to go in life, and staying together might mean a big amount of compromise -- which could hold you back from meeting your goals. This could occur on a basic needs level -- such as, one partner believes strongly in family and home, while the other wants to pursue a career that takes them to the far corners of the globe, alone.
Or it could occur at a more philosophical or intellectual level, with you pursuing a life path to which your lover is ethically opposed. You could have started out feeling as if your relationship had possibility, but as time goes on and you communicate more and more about yourselves, your beliefs and your dreams, you begin to feel less and less like you can relate to each other. At best, this influence between you might serve as the catalyst for you to figure out that, in order to pursue your true calling, you need to head in a direction that leads away from this person. How painful this is, and how difficult, is determined by other aspects between you and by the depth of your bond when the realization occurs.