It’s a simple principle, and yet so often overlooked or underestimated. Compatibility in a relationship isn’t just about being able to have a good time with someone. Of course it’s important to laugh together and enjoy each other’s company—to share interests and hobbies and values.

But compatibility is about so much more than similarities. Arguably, it’s more important to find someone who’s different from you in certain key ways. Because personal growth depends on being challenged, and you will not be pushed by someone who’s exactly like you.

If you want to grow, don’t date your twin.

It’s easy to be seduced by your mirror image—someone who validates your every whim, who agrees with you on every major issue, and who wants to spend every hour of the day just as you do. It’s reassuring to be strikingly similar to another human, but when you choose a mate who’s just like you, you’re destined to remain stagnant.

Parallels are comforting. They are warm and fuzzy and easy to mistake as loving. But they are not the seeds of growth. Sameness won’t expose you to knew things, or teach you all that much about life. The strongest couples aren’t made up of people who have identical views, personalities, or backgrounds. They’re comprised of people who offset each other and challenge each other daily to reach new levels of understanding and to experience new things.

Don’t date a “yes man” or “yes woman”—the people who laugh their faces off at everything you say, and who follow your lead blindly every day. Date the person you literally can’t stand on occasion because their opinions drive you mad or their way of seeing the world seems incomparable to you. Force yourself to try to see things from their perspective—to learn how their experience of the world has shaped their views and made them harbor whatever beliefs they hold dear.

Urge yourself to consider an alternate reality.

Date someone whose strengths offset your weaknesses, and vice versa. Someone you can admire for being truly accomplished in the areas you struggle in—who’s motivated where you’re lazy, meticulous where you’re sloppy, cool and collected when you’re given to craziness.

Your ideal match might not understand your sense of humor, exactly. They might wonder why you crack up at certain jokes, but there will be so much joy in explaining to them why you find something so damn funny. Your perfect partner might not want to watch the movie you’re dying to stream, but there will be so much happiness is nudging them to give that subtitled foreign film a go and witness their eyes well up a little (or not at all).

Your soulmate might complain as you drag them to an event they’re certain they’ll detest, until they realize that it’s not so bad after all. They might whine as you insist on teaching them how to snorkel, ride a motorcycle, or operate a chainsaw—until they’re smiling wide with pride because they’ve pushed their personal boundaries.

This person will round you out. They will pick up the slack you leave in your wake and tighten the way you play the game of life.

Together, you will be better. You will enhance each other’s lives, even though you will not always align. You will butt heads, and you will fight. But if you know how to apologize, everything will be fine.

Over time, you will learn to celebrate each other for exactly who you are, including those sometimes irksome differences. You will cherish the aspects of your partner’s personality that sometimes make you want to pull your hair out just as much as you appreciate the traits that overlap with yours.

You will come to understand that your partner’s flaws aren’t flaws at all. And neither are yours. You are both human and you are both constantly evolving. As a couple, you’ll see that you’re unstoppable—thanks to each other.