Relationships—whether with a partner, family, or friends—are funny things. On the one hand, most of us seek them out because, at heart, we’re social animals. We enjoy both physical and emotional intimacy. We want to be surrounded by people who get excited about our successes and whose successes thrill us in turn. We want sounding boards for new ideas, support in hard times, and the genuine joy that comes from shared experience.

On the other hand, relationships can be threatening. They call our behaviours into question, expose us to judgment, and frequently incite frustration and aggravation. Intimate relationships, in particular, are stellar at this. After you’ve been living with someone for any length of time, the things that can irritate you are quite astounding—the way the other person dresses or chews, whether or not they make the bed, the number of dishes that pile in the sink, the volume of the television.

What’s fascinating about this dynamic is that it’s actually predictable. It is, in fact, one of the greatest gifts of relationship. By making us uncomfortable and exposing our own weaknesses, relationships present us with constant opportunities for personal growth. And the way in which we respond to those opportunities ultimately dictates both the longevity of our relationship and the extent of our emotional maturity.

Starting at the same place

Here’s a secret about intimate relationships that not everybody knows: when you first get together, you tend to be at the same level of emotional development. Lots of us don’t like this idea. We’d rather believe our emotional maturity has always vastly exceeded our partner’s. It’s just simply not the case.

In fact, one of the main reasons we’re attracted to each other in the first place is because we’re starting at the same place. And we tend to start with a shared set of rules, even if they’re not explicitly articulated. Those rules determine the parameters of our relationship and revolve around the things we enjoy at the time. For instance, they dictate things like how often we go out at night, whether or not we exercise, the kinds of people we like to hang out with, the types of food we eat, and the kind of sex we have. Generally, at the beginning of a relationship, those interests align.

As we grow, however, our interests tend to change. Let’s say Partner A decides, for instance, that they’re tired of sitting on the sofa every night eating chips and drinking beer. They want to start exercising, cut out meat, take up meditation. Partner B should be excused for feeling a bit betrayed. I mean, this wasn’t part of the social contract, right? So now the couple faces a few choices:

Partner B can shame Partner A into abandoning the health kick. “Seriously, you look great the way you are. Why mess with what ain’t broke?” In this case, the opportunity for growth is lost—at least until one partner is ready to change again. If this pattern of shaming persists, however, the relationship will never evolve—likely resulting in boredom, apathy, monotony, and fertile ground for infidelity.

In a second scenario, if Partner A is committed to change, Partner B can still stay exactly where they are. “It’s your health kick, not mine.” This attitude, held long enough, will likely spell the end of the relationship. When one partner is evolving and the other is standing still, you ultimately grow apart.

Door #3 is the hallmark of a committed relationship. It’s where Partner B takes a deep breath and says, “Heck, I’m not sure I’m going to like this, but I’m at least willing to try.” This is where relationship begins to exert its positive influence on you. That spot where you’re willing to try something that makes you uncomfortable in service to strengthening your personal connection.

Evolving together

What’s awesome about this process is that it happens across the board, and can be initiated by either partner at any time. One partner may start the health kick, but the other one may drive a change in career or earning potential. One partner may encourage more travel, and the other might introduce more diversity into the bedroom. One partner may hold the space for having kids, and the other may make it possible to buy a new home.

This isn’t to say that evolution by one partner will always be sufficient to pull the other along. Fundamentally, we’re different people who will forever have divergent interests. The key to using your relationship as a catalyst for growth, however, is the willingness to at least try to match your partner’s attempts at evolution. This isn’t only how we grow. It’s how we grow together.

If you’d like to learn more about how this all works in practice, I recommend the book Passionate Marriage by Dr. David Schnarch. Go ahead, try it. You may even like it.