There’s a saying in Spanish. Those who sleep with children wake up pissed. One of my students taught it to me. She was doing a study abroad at my university, and used the phrase in a paper. Basically, it means don’t date someone who can’t even adult.

It’s probably the greatest proverb on dating I’ve ever heard, and it helped me make a big change in my own life. You see, I’d been dating something of a man child for almost a year.

In fact, I’d been fighting for him. We weren’t officially engaged, but we were talking about marriage. We’d gone through some rough patches, but I thought we’d turn out okay. A single little aphorism from a student paper helped me realize what a mistake I was making.

How immature was he? Well, he once threatened to break up because I gave another guy a ride home from brunch.

We’ve all probably dated someone on the immature side, only to regret the outcome. We overlooked other shortcomings in favor of their looks or charm. When things started going south, we told ourselves to fight to save the relationship. This message repeats throughout our culture. It’s an exhausted trope in romantic comedies.

But we shouldn’t have to. A relationship we have to fight for isn’t worth saving. Fighting is the wrong word.

We have to do a lot of things to make a relationship work. Compromise. Communicate. Invest. The list gets long, but it should never include fighting. If you’re fighting to keep someone, you should consider letting them go. They’re probably not worth the trouble.

That sounds cold, but you’re doing them a solid. The person you’re dating now will never change without a catalyst.

You can be their wake-up call.

If not, at least you’re freeing yourself up to find someone who’s willing to invest in your shared future.

In my 20s, I dated cheaters back-to-back. When the truth came out, my friends always encouraged me to “fight” for my relationship. Assert myself. Do whatever it took. Dumping people for cheating was out of style back then. You were supposed to stand up for what you wanted.

Each time, I did. And I always won. My exes realized their screw-ups and came crawling back. Sure, their surrender was validating. But also destructive. Nobody’s love is a spoil of war.

Cheating can signal a wider problem, something you can both work on and struggle through together. But not always. Sometimes your partner has brought their own bag of problems. You can’t fix them by making yourself prettier, smarter, or more emotionally available.

Your partner has to love the you that exists in front of them, not some future version with upgrades.

They can’t waffle, either.

The courtship stage can’t last forever. Eventually, you’ll both go through periods where you just want a hand to hold in the park, someone to watch Netflix with. You’ll stop performing for them, and that’s when you’ll see the true strength of the bond you made.

Towards the end, I got tired of having to prove myself over and over. The exhaustion hit me in the face one weekend at a party. That’s where I watched my future-ex flirt with another girl for almost two hours. We were supposed to go dancing later. We didn’t.

By the time he finally packed up his game, it was midnight. He apologized profusely to me in the car. Time had just gotten away from him. He asked, “Do you still want to hit the club?”

“Not really,” I said. “I don’t feel like dancing anymore.”

He tried to tease me. “Don’t pout.”

“I’m not,” I countered. “I’m tired.” When I said that, we both knew I was talking about the big kind.

Some of my friends described my strategy as passive-aggressive. They said I’d helped create and condone a space for him to seek someone else’s attention. They asked me why I didn’t just butt into his conversation with another girl and then drag him off to the club.

In short, they thought I should’ve stood my ground. My answer was simple. I’d already done that. How many more times would it take?

After six months, maybe it was finally up to him to regulate his own behavior. Maybe he needed to show me that he could go two full hours without getting distracted by a shiny new girl.

Of course, we’d already had those conversations.

We finally broke up sometime after his birthday party. His new friend showed up, and couldn’t keep her hands off him. She had plenty of opportunities, because I was the one helping his parents with snacks, pouring drinks, stacking presents, and storing coats.

Every time I turned around, she was hugging him from behind or kissing his cheek. A friend caught me glaring at them. She thought it was hilarious. “You looked possessed,” she said.

Later, my future-ex and I had an argument about the party. He apologized, and even admitted his new friend was out of line. But he had to add, “If it bothered you so much, why didn’t you say something?”

And to think I’d also been coaching him on graduate programs, CVs, and networking. That’s when I realized what I’d become. Not a girlfriend, but a mentor with benefits.

There I was, waking up pissed. Increasingly, it got hard to see him as a partner. He tried to redeem himself with superficial gestures toward adulthood. He talked a lot about grad school, but never applied. He considered re-taking some college courses to replace Fs and bump up his GPA. But he never enrolled. He wondered about getting a better job with full hours and healthcare. But he never searched.

For a little while, I tried to help. I sent him job ads and advice columns on preparing for grad school. We held strategy and brainstorming sessions. This was me fighting for the relationship, by trying to invest in his future, which I misunderstood as our future. But there was no point in me investing in us, if he didn’t invest in himself.

So I ended our future, over coffee.

If we were a romantic comedy, then my future-ex would’ve had some life altering epiphany after the breakup.

He would’ve tried to win me back.

He would’ve seen that I made him a better person, and he would’ve fought to keep me at all costs.

He would’ve pulled some ridiculous stunt to prove himself.

I’m so glad he didn’t.

In romantic comedies, getting dumped usually lights a fire under the main character’s ass. They pull themselves together and transform into their best self. They go to war for their true love.

But real life doesn’t usually play out like that. In reality, the hopeless screw-up doesn’t really change. They put on a show for a few days, or weeks. Then things slowly return to normal, then get worse.

That’s how unhealthy relationships linger for months and years longer than they should. We fight without asking why. Or we expect someone else to fight for us, and maybe they can. But should they?

After the breakup, my friends showed full support. Some of them admitted they’d just been aping what they saw in movies. A few had even tried to tell me the truth all along, and I just hadn’t been listening.

My current partner and I have stayed together five years now. We’ve endured some rough times — long distance, crappy apartments, sub zero temperatures, job insecurity, and at least a few canceled flights.

We’ve also endured hours in the car, listening to each other’s music.

We’ve only fought for each other in the sense that we’ve fought on behalf of one another. You might also say we’ve fought alongside each other. But never to win the other person.

Fighting offers terrible metaphor for partnership. You can never “win” someone else. There’s no external enemy. No guns, switch blades, or Kevlar. We just think there is, when the answers run out. Stop fighting. Instead, invest. If your partner won’t do that, then say goodbye.