Whatever factors or forces may bring you together in the beginning, over time you'll begin to notice a frustrating lack of basic connection. You simply won't feel attracted or attached to each other in that all-important way; your sexual connection will likely cool off prematurely, and you'll both wonder what, exactly, is holding you together. You may have particular trouble admitting that there is a problem between you, being too committed to pretending everything's fine.
Your partner, on the other hand, will be able to sense that you two aren't going to those passionate depths together, and they may try to force the raw, intense interaction they crave, which also won't work. Rather than pushing at each other or trying to exert control over the situation, it will be far better for both of you to stay calm as you talk out your true, honest feelings. You'll likely discover that whatever animal magnetism you felt in the beginning is based more on a past-life connection than on anything in the present; perhaps that's why it will fade quickly, the way a shadow fades into the night. This doesn't have to be a deal-breaker, however; if the relationship is important to both of you, you can agree to work on making your physical connection, and therefore your overall bond, stronger through honesty and through transforming the way you connect at an emotional level. Once you can do that, the physical level will follow.