I even go so far as to say that God has designed conflict in marriage.
Yes, God desires that we all live in harmony, but that doesn’t mean we will live in an environment free from all conflict (or trouble).
But conflict itself is not sin.
God designed us with differing preferences. In marriage, husbands and wives have different preferences that are not sin issues…they are simply differences. How we deal with these differences can lead to sin rather than harmony….but having differences (i.e. conflicting preferences) does not mean we aren’t living in harmony.
It is how we deal with those conflicts that will either lead to harmony or sin.
In 1 Corinthians 7:28 the Apostle Paul says that we will have "trouble" if we marry. Marriages bring trouble. That comes as no surprise to those of us who are married! But Paul does not label this "trouble" as evidence of sin or the result of sin per se. His very point is that if you marry, you have not sinned.
In other words, marriage brings troubles, and those troubles are inevitable. If you marry, get ready for troubles. He does not pass judgment on this trouble as evil or sinful.
So what does he mean by trouble? Earlier he illustrated exactly what he means by trouble. Every text has a context!
1Co 7:3 The husband must fulfill his duty to his wife, and likewise also the wife to her husband.
1Co 7:4 The wife does not have authority over her own body, but the husband does; and likewise also the husband does not have authority over his own body, but the wife does.
When saying the husband does not have authority over his own body but the wife does, and the wife does not have authority over her own body but the husband does, he is talking of the sexual relationship.
What is Paul saying? Paul is getting real. Paul is saying, to paraphrase, "Look, you are going to have trouble in your marriage when it comes to sex. On Tuesday night when the husband wants sex and the wife does not want sex, who decides? Get ready for trouble. Or, if the wife wants sex and the husband does not want sex, who decides? Get ready for trouble. In this text, both have equal authority in the sexual realm.
So - some, not all, conflict or trouble is the result of God's design and is in keeping with his will, and therefore we should not freak out when it happens. This is the good news. We should not panic, feeling we made a mistake in marrying this person because we have these ongoing troubles. If these troubles are not evil but the typical conflicts day by day, you are very much in God's will.
Don't bail out. Don't say your marriage isn't working because of these frustrations. Instead, focus on dealing with those conflicts in a way that leads to harmony, not sin.