You dominate this person's dreams, their sexual energy, their waking life and their imagination. You have a strangely magnetic hold over them, and as long as you're both open and honest about your own position in the relationship -- whether or not you want things to be serious, for example -- this influence should make for a positive, even transformative experience for both of you. Be aware, though, that this relationship probably takes on an all-or-nothing quality.
If you're not both on board regarding a commitment, things could get pretty complicated. Any lack of devotion on your partner's side, especially, leads to you getting possessive, jealous and generally hard to deal with. So if they're not in the relationship heart and soul, they should be upfront about that fact -- and you should let it go instead of fighting tooth and nail to keep something alive that's just not working. If you are both in it for the long haul, let each other know that as well. If this relationship is a long-term one, you both must exist within it knowing that you both have to make some adjustments within yourselves for the good of the relationship. As long as you treat each other with the honesty and respect that you each deserve, you develop an overpowering love that is a great source of sustenance for you both.