Perhaps one common cultural assumption Christians may have regarding marriage, is that true happiness begins and ends with the married couple itself. I do not think that the Bible condemns the pursuit of happiness in general, or in particular. Instead, with regards to true and Biblical happiness, the Bible assumes that we pursue it. For example: “Love your neighbor as you love yourself.” Regarding the married couple (and, the husband in particular), Paul says, “Husbands should love their wives as their own bodies. He who loves his wife loves himself.” I am assuming that in the act of loving oneself or another, the lover is the pursuer of happiness. I believe that the thesis of Gary Thomas’ book, Sacred Marriage is right depending on his definition of happiness. His thesis question: “What if God designed marriage to make us holy more than to make us happy?” From what I’ve read of his book so far, I am assuming his definition of “happy” in this thesis question is the idealized definition many Christians have taken up from our culture’s own cues. So, with this definition in mind (but going with the Bible’s definition), I’d say that God designed marriage to make us holy (i.e., as he is holy) that we may be happy in him–who should be the beginning and the end of our happiness/love as married couples.
Maybe one of the biblical characteristics of marriage that people might treat as being purely cultural (as during the apostle Paul’s time and culture), pertains to gender roles in marriage. Paul says at least four things in particular here (Eph. 5.22-33): 1) Wives, as submitter to their own husbands; 2) Husbands, as head of the wife; 3) Husbands, as sacrificial lover for their wife; 4) Wives, respecter of husband.
I believe that the greatest threat to marriage relates directly to the misconception of true happiness, as discussed above. Marriages end, not because one or both of the spouses aim for happiness and miss. Instead, marriages end because one or both of them aim at the wrong (i.e., idolatrous) things that inevitably lead them to ruin and misery.
I believe that many couples treat marriage so lightly, that their own marriages dissolve so quickly, because they treat God and his word so lightly. Every little thing and every big thing that we do, think, feel, say, and are, is God-relational. And, when a husband and wife seem to dismiss God into the peripheral areas of their lives, they cease to love each other as they ought. A husband cannot love his wife properly unless he loves (i.e., finds joy in) his God rightly.