Wintery Knight blog:

There is one big reason to worry about the quality and longevity of people’s intimate bonds. It is that relationships often produce children, and children are profoundly affected by how their parents get on.
You could make enough confetti for a summer of weddings with all the academic papers that show how much children gain from being brought up in stable, loving families, and how much they suffer when those families break down. Culture and customs make little difference. In Japan, four-fifths of single-parent households emerge when couples divorce—a much higher share than in the West, where people usually slip into single parenthood without marrying. Japanese children living with only one parent nonetheless perform significantly worse in school tests, just as children from single-parent families do in Europe and America. In poorer countries, family breakdown can kill. According to one recent estimate, the chance that an African child will die before turning five is about 25-30 per 1,000 for those born into stable families, but 35-40 per 1,000 for the children of single, divorced or widowed parents.
Marriage is not always good for children. They do not benefit when a parent marries somebody who is not their mother or father, and seem to suffer if the parent they live with cycles through several relationships. What they seem to need most is for their biological parents to stick together. And one strong claim that can be made for marriage is that it appears to glue parents together more tightly than any other arrangement.
This part is key, especially for those millennials who think that cohabitating before marrying makes the marriage more secure:
Analysis of one large American data set by Kathryn Edin and Laura Tach, two sociologists, shows that 27% of marriages broke down within nine years of a child being born. By contrast, among couples who were merely cohabiting when a child appeared, 53% separated within nine years—and most of the remaining 47% were married by that point. Among couples who were dating but not living together when the child was born, 81% had split up.
Again, this pattern runs across national and cultural borders. Cohabiting couples behave a bit more like married couples in countries where giving birth outside marriage is very common, such as Estonia and Norway. But they seldom attain the same level of stickiness as married couples, even after controlling for the mother’s level of education.
Cohabitation doesn’t work, because it’s basically saying that I’m going to try the other person and see if I like the other person, and that sex is required to know if I like the other person. It doesn’t really matter that you know the other person really well, because you can always get out of cohabitation just by leaving. Marriage says that I’m going to commit to the other person for life, through thick and thin. Here, both people tend to do a more thorough job of selecting their partner, perhaps even consulting fathers for advice. Why? Because getting out of a marriage is a lot harder to do, and more expensive.
In the past, I’ve blogged about some factors that can make your marriage pretty much divorce proof: things like chastity, not spending too much on the wedding, age of the man and woman at marriage, education levels of each spouse, number of people attending the wedding ceremony, isolation from other divorced people, church attendance, and so on. The truth is that you can engineer a marriage that’s practically divorce proof. But if you insist on spontaneity and following your heart, then you aren’t going to care what studies say works best. A stable marriage takes preparation, and that means making pro-marriage choices all throughout your life before your marriage, instead of doing what feels right to you in the moment. What feels good in the moment is almost never the right choice if your goal is a stable marriage.