It’s simply a fact of life that not all relationships last forever. Some flourish while others wilt. But it’s not just a matter of luck that makes some relationships more successful than others.

Recently, scientists set out to explain why some partnerships thrive and some fail through an extensive study of 11,000 couples.

According to their findings, the number one thing that makes a relationship successful is perceived partner commitment.

The meta-analysis, published in July in the Proceedings of the National Academy of Sciences, used 43 earlier studies, aiming to “quantify the extent to which relationship quality is predictable and identify which constructs reliably predict relationship quality.”

Based on the results, it was clear that people who believed adamantly that their partner was committed were the most likely to have a thriving relationship.

In the case of the research, which was led by Western University, commitment was defined as one partner feeling confident that the other was committed to making the relationship work forever. And it beat out trust, passion, support, affection, and sexual frequency as the most essential predictor of a strong relationship.

But it’s not only commitment that matters. Beyond that, these are the top four strongest predictors of a successful relationship, according to the study.

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1. Appreciation

Appreciating what your partner adds to your life was the second most significant predictor of a strong relationship.

2. Sexual satisfaction

How satisfied you are in bed is a significant predictor of how healthy a relationship is. An unsatisfying sex life is often a symptom of another issue within the relationship.

3. Perceived partner satisfaction

Knowing and understanding that your relationship makes your partner very happy can predict the success you two will have together.

4. Conflict