What makes a good marriage? It’s a question that everyone has thought about, whether they’re newly engaged, married for 30 years, or somewhere in between. Some might say you must find ways to serve each other, putting your spouse’s needs before yours. Another person might add that you should remember you and your spouse are on the same team, and you should fight for your marriage together.

Someone else may add that you should share each other’s passions, which are all true. You may believe the key to a successful marriage is other things like sexual compatibility, good communication, or not having money issues. Of course, all of these things matter, but when it comes to predicting long-term stability and satisfaction in marriage, kindness is what matters most.

Kindness doesn’t only mean bringing your spouse a cup of coffee in the morning. Studies show that having a generous mindset and appreciating your spouse’s intentions, even if the execution is off, is essential. For example, your husband might not have been intentionally trying to irritate you by leaving the toilet seat up; he could’ve just forgotten. Perhaps your wife wasn’t late to dinner on purpose, but she had to make a few stops beforehand.

Instead of being on the lookout for your spouse’s mistakes, look for things you can appreciate and say “thank you” for. Be intentional about showing respect. In humility, as Scripture says, value your spouse above yourself, looking not to your interests by to theirs. Here’s the thing about kindness: It is not something we have or don’t. The Bible says kindness comes with our salvation as the Holy Spirit transforms our hearts. “The fruit of the Spirit,” Paul writes, is “love, joy, peace, forbearance, kindness, goodness, faithfulness, gentleness and self-control.” Kindness is available to us all, like all of these other God-given attributes.

It works like a muscle, getting more robust with use and stronger with prayer. According to a Wall Street Journal article a few months ago, prayer makes a difference, even when one or both partners are unkind. “When people pray for the well-being of their spouse when they feel a negative emotion in the marriage, both partners – the one doing the praying and the one being prayed for – report greater relationship satisfaction.”

If you’re annoyed with your spouse – they left the toilet seat up, were late again, did whatever – don’t get mad. Try praying for them instead. You’ll both be happier.