In the past -- perhaps even in a past life -- you were overly selfish in your relationships, always pursuing your own aims and pleasures regardless of the other person's feelings about it. You were argumentative instead of cooperative, because you believed in the old 'my way or the highway' method of getting things done. But this approach probably didn't win you many friends or much closeness.
Now, however, you've got a chance to become much more of a negotiator and a cooperator in your relationships, instead of a competitive, me-first fighter who always has to have everything your way. Learning to share is one of your primary lessons in life, and what better arena to learn it than in an intimate, committed relationship? Harmony should be your goal with your sweetheart, not coming out on top all the time. Though creating and maintaining that harmony will definitely be difficult at times, doing so will make you a stronger, more well-rounded and diplomatic person in the end, and will definitely make you a better partner in love. Your intimate relationships will also stand a much better chance of lasting for the long haul if you can learn to cooperate more.