Everyone wants a soulmate, right? Sure they do! Here's the thing, though: that "perfect" match may not be the mate that's your best partner in this life.

Let's start by getting our definitions clear. Here's how Wikipedia defines soulmate: it's "somebody with whom one has a feeling of deep and natural affinity, love, intimacy, sexuality, spirituality, and/or compatibility." A soulmate is a partner who feels right, through and through. With a soulmate, everything is improbably easy. There's no noise in the signaling: your cues are picked up, and honored, as they were intended to be. A soulmate feels like your "missing half." He or she makes you feel complete.

It's a beautiful dream, and one that animates much if not most of our romantic questing. Unfortunately, the dream of the perfect partner is, well, imperfect.

For one thing, issues arise even between soulmates. There was never yet a relationship that came completely free of tension: there are no "soulmate exemptions." Second, and even more fundamentally, the best and highest purpose of relationship may not be to get along well, with a minimum of disruption. In fact, it may be precisely the opposite--to challenge us to grow beyond our current limitations.

And this requires a measure of conflict, unhappiness and tension. Banal though the term has come to be, "personal growth" is something real and valuable. We are always becoming; ideally we are always becoming more. We are becoming more wise, more integrated, more complete. Personal growth thus defined is one of our life missions--and it is also a mission of relationship. David Snarch, author of the book Passionate Marriage, calls relationships "people-growing machines." It's an interesting and provocative term. When we rub up against our partner (and not in a way that feels good!), we are being offered an opportunity: to become more than we were.

Relationships can collapse because of too much conflict, and also because of too little. Yes, Virginia, there is an unhappiness trap: it can be wise to get out when the going gets too painful. But there's also a soulmate trap, and as unlikely as it may seem, it can also be the path of wisdom to get out when the going is too easy.

The best relationships produce pearls out of the grit of conflict--and leaven the challenges with large and frequent doses of laughter, humility and love.