The attraction between you is so strong and exciting that it could have inspires you to jump right into a full-blown relationship before you knew each other very well. For your lover especially, the attraction could be based on a sense of unpredictability and excitement that isn't sustainable for a long-term relationship. Things between you feel exciting, new, unexpected and unique.
Your interactions are spontaneous and lead you places you don't expect to go; you're social together, and you blend your groups of friends. That's all fine and dandy, at least until things start to go awry. At best, this aspect keeps things interesting, but it's likely that interesting fast becomes uncomfortable for your partner. They aren't able to count on your bond; you probably have a hard time committing to them, and you might even find that your feelings toward them change as fast as a pendulum swings. You need a lot of space, and even if your lover does too, it isn't often at the same time, so your rhythms are off in terms of your romantic needs. After some time, you could start to seem unreliable as a partner -- showing up late for dates, canceling plans at the last minute and so on -- even if you don't mean to. None of this fosters any feelings of groundedness or unity, and the relationship could end prematurely unless there are other aspects between you to promote a feeling of being settled and satisfied.