In another lifetime you were embroiled with this partner in a relationship that brought out the worst in each of you in terms of power plays and struggles for domination. In this life, that old, unconscious anger toward this person is still present within you, and it will make itself known if you're intimately involved with them for any length of time. You'll find that you feel resentful toward them for no reason that you can pinpoint, and whenever they assert their independence or push toward goals that are unexpected or unappealing to you, you'll likely feel jealous or worse.
Even though logically you understand that you're two separate people with unique ambitions and destinies, you'll still feel as if your partner's attempts to move forward along their own path are somehow a threat to you. It will take lots of kindness, temperance and open communication to move past this issue, since it's so unconscious and deeply rooted in the distant past.