The five stages of a relationship are the Merge, Doubt and Denial, Disillusionment, the Decision, and Wholehearted Love. Every single relationship moves through these five stages—though not only once.

Think of these stages not as steppingstones to a final outcome but rather as a series of seasons that we move through in an eternal cycle.

We often think all intimate relationships reliably progress from the initial meet-cute to giddy infatuation, to a series of small trials and tribulations, and finally to a blissful state of happily-ever-after.

It's a satisfying narrative we see all the time in the movies, TV, and music. In reality, love is a journey without a final destination.

We shouldn't expect that at some point in our relationship, we'll look back at the obstacles we overcame and say, "Well, that's it! We're here! We made it!" Because beyond wherever you are now, another hurdle awaits.

In other words, the stages of a relationship are not linear but cyclical. Even people who reach the fifth and final stage of a relationship—Wholehearted Love—will eventually find themselves looping back to Stage 1 to start the process all over again. But they can always find their way back.

This Love Cycles model is drawn from my experience as a couples therapist for the last three decades, studying couples at all stages of a relationship and identifying common patterns.

The first stage of a relationship is the Merge, aka the honeymoon phase. It's the initial, sweeping romance that often consumes a couple when they first get together, including an all-consuming joy in the presence of our partner and insatiable, passionate sex.

Often people in this stage of a relationship will feel as if they've found their "perfect match," someone who is so eerily similar and compatible with them. They feel they always want to be together, and boundaries often melt away. The two seem to merge together, or at least feel eager to do so.

These emotions often drown out the rational part of our brain. Indeed, research tells us this first stage is marked by biochemical changes in our brain1—a cocktail of hormones that trigger and maintain a state of infatuation, such as dopamine, oxytocin, and endorphins.

Enjoy this stage to the fullest—this is the stuff that makes dating so delightful and intriguing. At the same time, be aware of your heightened emotions. Take time to step back and observe your emotions and your relationship, and actively question whether this person really is the best match for you.

Get candid advice from friends who can make sure you're not missing any truly worrisome red flags while under this biochemical love potion.

Go slow with making any big decisions, too—the Merge can fog your vision and make you want to dive into situations that might not actually be wise or healthy for you in the long run.

In general, don't make decisions because you're "so in love"—because that's a temporary feeling of infatuation that will eventually fade.

The second stage of a relationship is Doubt and Denial, in which we finally start to actually notice the differences between us and our partners. We wake up from the trance of infatuation with a thump, finding that the same qualities that once seemed so perfect have begun to annoy us. (His reliability now feels rigid; her generosity seems irresponsible; their adventurous nature feels like unnecessary risk.)

And unfortunately, friction is natural once we run up against each other's differences. Power struggles increase, and we marvel at the change in our partner. Feelings of love mix with alienation and irritation. Perhaps we're not "perfect" for each other after all.

As our disappointment escalates, so do our biological responses to stress. Depending on our personality and circumstances, we may want to fight or to withdraw.

At this point, the skills of conflict management are essential. Learn how to deescalate conflicts and face relationship problems head-on while treating each other with care and respect.

Remember that power struggles and arguments are normal parts of a relationship; they're not necessarily a sign that love is ending or that the relationship isn't working.

You'll need to learn to identify the difference between healthy disagreement and unhealthy control issues; the former can be worked through, while the latter may be a sign you should break up.

Because this is the stage where you're starting to recognize your differences, this second stage of a relationship is also a good time to learn your love languages. There are five love languages, and it's important for each person to know how their partner wants to receive love.

The third stage of a relationship is the Disillusionment stage. This is the winter season of love, one that may feel like the end of the road for some couples. At this point, the power struggles in the relationship have come fully to the surface; the issues the couple have consistently shoved under the rug are now glaringly obvious.

Some people become perpetually vigilant, ready to fly into battle at the slightest provocation. Other couples might quietly move apart over time, putting less and less energy into maintaining the relationship and investing more outside of it.

Clear the air and create space. Stop pushing problems under the rug and avoiding issues; as tiring as the repetitive arguments may feel, pushing them under the rug just leaves a lumpy carpet with much to trip over.

There may be a lot of negative energy in the relationship at this stage. To offset this, practice showing affection even when upset. Can you feel angry and be aware that something isn't working that you need to talk about—but still go to dinner and a movie together?

During the Merge, the brain notices only the positive and avoids anything that challenges that view. In the Disillusionment stage, the brain is zeroing in on all the relationship's deficiencies.

The fourth stage of a relationship is called the Decision because you're at a breaking point. Emotional breakdowns, leaving the house for hours to get away from each other after a fight, and self-protective behaviors are all commonplace. So, too, is indifference and remoteness.

You know you're here when you begin to seriously contemplate leaving and even make plans for exiting the relationship. You may feel ready for an enticing new beginning with a new person.

When I see couples at this stage, I always encourage them to consider taking a new path, which is to decide to do some work before making a choice about the relationship. Many times, couples feel they want out of the relationship, but when they learn the skills to communicate effectively, years of resentment or estrangement can fade away.

Doing the work involves understanding your own role in your relationship's deterioration and committing to real change. If we make this last choice, we can learn the lessons that will help us become the best people we can be as we give our relationship the chance to grow and deepen.

Even if couples do make the choice to part ways, they can often do so in a constructive way, wishing one another well and understanding their own part in what happened.

The fifth stage of a relationship is Wholehearted Love—when our relationship is at its healthiest and most rewarding. It's love's summertime, when the fruits of a couple's labors are fully ripe and ready to be savored. Couples experience true individuation, self-discovery, and the acceptance of imperfection in both themselves and their partners, recognizing there is no such thing as a "perfect match."

There's hard work still involved in this fifth stage of a relationship, but the difference is that couples know how to listen well and lean into uncomfortable conversations without feeling threatened or attacking one another.

Nourish yourself. The Wholehearted Love stage is fueled by the qualities of two wholehearted people: generosity, humor, flexibility, resilience, good boundaries, self-care, and a life with meaning and purpose.

Couples are able to stay in this stage as long as they're able to continually sustain their own wholeness as individuals, so make self-care and self-growth continual goals.

Know that there will be new challenges waiting somewhere in the distance but that you can be well-equipped to deal with them when they come. In the meantime, relish the journey.