You'll be quite attracted to each other, especially on a physical level, but you'll also hit old karmic chords within one another that draw out your more impulsive qualities. You won't feel able to rely on this person, and that will upset you even as it excites you. Their unreliability will be like a fever under your skin, just as it was ages ago, in another time and place, when you two loved fast and hard but not for long.
You also may have shared an adversarial connection in a past life, because that dynamic will also come out again in this one as you try various tactics to boss this person around and box them into something more controlled and understandable. But if you think about it, you may realize that controlling them, and quelling that wonderful, unique, spontaneous energy of theirs, is the last thing you really want to do. That urge simply comes from an old, long-suppressed place within you that really has no bearing on the present. Once you begin to recognize that, you'll not only be able to give your partner more freedom, you'll also free yourself up to pay attention to more interesting and less upsetting things -- such as how excited this person makes you feel on a daily basis.