I was also thinking about my apartment, which is falling apart. There are doors that don't work properly, bathrooms that need plastering and repainting, a kitchen wall that needs to be re-done, a leaky valve below the sink. It's not that we live in a slum, but that we live in a building built in 1933. Over a long period of time things need replacement; things you never knew existed suddenly emerge as problems. As in a marriage, a certain level of maintenance is required to make life liveable.
When something goes wrong with the house I assume we have to fix it, or I say,
I think part of it is that we hold in our minds an ideal of marriage, and it doesn't include real flaws (like the kind you and I and our spouses have). Our ideal doesn't factor in grinding long-term difficulties, nor deep disappointments, nor frustrating I-don't-know-how-to-make-this-better problems. And yet, realistically, what can we expect? Marriage involves another human being.
Our wealthy society places huge emphasis on being happy, in part because we don't have to expend a huge amount of effort on survival. Happy is good; I like being happy. I like it when my kids are happy. I like it when my husband is happy. But unhappy things happen if we set happiness up as a god. We neglect less comfortable but important goals like the hard work of becoming a better person, the unselfishness of contributing (significantly) to the welfare of others, learning how to be at peace in the midst of awful situations, doing the right thing even when it hurts.
For most of us, the important lessons in compassion, how to make sacrifices, rebounding from setbacks and suffering, resourcefulness, and being true to what we believe don't come from happy times. They arise almost exclusively from situations we never would have chosen for ourselves. In short, we grow more (or can grow more) through challenges than through happiness.
I love my husband. He loves me. Few flaws are fatal, either his or mine. Most are simply cracks through which we can learn to love differently, better, deeper, more. If we're patient enough. And if we believe that the reason we're together is because that's how it's supposed to be.