What are the things that threaten marriage besides the obvious (money problems, infidelity, etc)?

I recently read an article that reported on a couple of long-term studies, and there were two factors we don’t usually think of: children, and boredom. Two hundred couples were studied eight years after their wedding, and 90% said that they saw some decrease in “relationship satisfaction” after having children. 

The couples who were more “romantic” before they had children felt it more acutely. The kids cut into their time together. Couples whose relationships had an added dimension of friendship seemed to do better. But the bottom line? Those who made time for themselves on a regular basis – just the two of them – fared better.

Boredom isn’t always easily solved. It can be insidious, and one day a husband or wife just realizes they’re bored – with life, with work, with their spouse.

My own opinion is that you have to be conscious of this kind of erosion and work against it. The experts say that the way couples can do this is to stay close to each other. They should try new activities together – taking a class, traveling to new places. In other words, they should try to be friends. Meet for coffee. Go out to lunch together. Schedule an overnight at a bed and breakfast somewhere.

A weird predictor of marital happiness is the old photo album. Researchers looked at childhood pictures of people and rated their smiles. And those who had the most intense smiles tended to be the most happily married. They don’t know why – perhaps it’s because the smiley ones are more positive people and attract positive people to them. Or maybe they’re just more compliant types, and want to please the photographer when he says “Smile for the camera!” Who knows?

I’m no expert, but I’ve been happily married for 28 years. And I have a lot of friends who’ve been married as long, or longer than me. There’s no easy answer. Even the studies can’t really pinpoint what goes wrong or what goes right. So much of it is pure chemistry, completely un-definable. What do you think? What is the most important part of keeping a marriage healthy?