Sometimes we get involved with people who, usually unintentionally, sap our strength, our will and ability to be fully and completely ourselves. Our first priority should be to ourselves, to pursue our own growth and edification in life, but sometimes we get involved in a relationship that impedes that growth. Unfortunately, this is probably that kind of relationship for your partner, especially.
Even though you have good intentions at the outset, things gradually devolve into a bitter power play. You could try to dominate them, just as a way to gain control over a situation that feels out of control. Or you could have trouble making a good sexual connection, which undermines the strength of the whole relationship. There is an unhealthy quality to your bond; jealousy probably plagues you, and any attempts at individuality, independence or personal growth on your lover's part are squelched. The trials they go through in this relationship probably stay with them long after it's over; they could feel traumatized by the sense of domination, resentment and subtle destructiveness that permeates your bond. It's probably unnecessary to point out that this type of relationship usually doesn't last long-term. If it does, you should try your hardest not to treat your lover in heavy or controlling ways, and to encourage them to grow as an individual.