While some Christians might be tempted to create a false divide between theology (perceived as sacred) and practice (perceived as secular or at least unrelated), that simply does not work. There is no such thing as a secular-sacred divide! Theology always affects practice. As a smart guy might say, “Orthodoxy produces orthopraxy,” which simply means that right belief will lead to right living. This is true of every area of life, and it is especially true in regards to marriage.
What a person really believes about marriage will always play out in their marital relationship. If a man really believes that he is only obligated to his wife as long as she stays in good physical shape, then he will eventually demonstrate this belief by leaving or looking elsewhere (adultery, pornography, etc.). If a woman really believes that she is only obligated to her husband as long as he provides an acceptable lifestyle, then she will eventually demonstrate this belief by looking elsewhere too. These are just two examples, but one could list many. The point is, what a person truly believes will affect how they live.
The Bible argues that marriage is instituted and regulated by God (Gen. 2:24; Matt. 19:3-12; 1 Cor. 7:1-16; Eph. 5:22-33). In fact, the Bible demands that all people everywhere honor God’s design and regulations for marriage (Heb. 13:4). This more than implies that Christians are not the only ones who are responsible before God to live according to a particular standard of belief about marriage. Furthermore, it is the Christian’s duty and privilege to live as an example of such right belief, no matter what is going on in the world around them.
You live what you really believe, and the world around you is watching…
“Keep your conduct among the [non-believers] honorable, so that when they speak against you as evildoers, they may see your good deeds and glorify God“ (1 Peter 2:12).