You started out strong together, with a vital and passionate connection. But soon you both started to notice that you're arguing or struggling against each other more often than you're actually working together. Your lover is a high-energy, dynamic, creative, passionate person, and it would seem like bringing those energies to your life could only be a good, exciting influence.
Except in this case, their energies end up being too much for you to handle. Your relationship could become more like a tug-of-war than a romance, with each of you -- and your partner, especially -- yanking mercilessly at your own end of the rope. They challenge you relentlessly, and not in a positive or growth-oriented way. They could lose sight of the fact that this is supposed to be a relationship, not a competition! You're supposed to work together as a team, not act like two opposing teams who taunt each other from the sidelines. Needless to say, all this excessive energy and aggression can lead to plenty of arguments, in which you both probably try to represent your own point of view instead of listening to your partner and responding to their needs. If you allow this aggressive energy to continue for too long, the relationship could be lost. It's hard to commit to something that's more work than fun, and after a while, that's how you both come to see it.