Ask anyone what they think keeps a relationship strong, and they will probably tell you it’s love. There’s some truth to that: love is what draws us together in the first place.

But after years of studying couples as a psychologist, and as a husband, I’ve realized something that research keeps confirming: The real factor that keeps couples together, long after the honeymoon phase fades, is compromise.

Psychologists define love as an emotion. And like all emotions, love fluctuates with stress, sleep, health, and the thousand of other factors that shape our daily lives.

So you can love your partner deeply and still get annoyed, frustrated, or angry with them. Love won’t shield you from conflict, nor will it solve your disagreements.

That’s why even the happiest couples argue and have rough patches, regardless of how much love they have for each other. The difference is that strong couples know love can’t fix everything — but compromise can.