Is it that marriage itself is beneficial or that people capable of maintaining a relationship make better parents? Divorce is significantly more common for bipolar, paranoid, and schizophrenic people for example. So I think we need to look at widows or something to control for those kinds of issues.
I was wondering about that, too. The data are very clear: if you grow up with married parents, you will do better. But, should everyone be rushing off to get married, or is marriage selective for people who will do better? Or is it partly selective, and also partly forcing yourself to work through a marriage makes you a better person?
These same people, when they find a suitable spouse, are more likely to tough it out when things get unpleasant in the belief their spouse is fundamentally a good person.
In marriage just like at work, you don’t judge someone by one event. People may have a bad day. Or they are sick and not themselves. Instead you should judge their actions over a long period of time. If someone has always been there for you, appreciated you and delivered what they promised, and for some reason hurt you today; you are more likely to give them the benefit of the doubt.