Conflict is a natural and normal growing pain of any maturing relationship. When two people— often two very different people—live together as husband and wife, differences and opposing opinions are bound to poke their heads out at some point. Conflict is not a problem, nor is it a sin. The way we settle it, however, can quickly become both if we allow the flesh to be in charge.
We cannot state it often or plainly enough. Marriage is the clearest sermon of the Gospel which can be preached. Our society has been rather successful at introducing us to strange notions of marriage, then convincing us that these strange notions that they attempt to call marriage are actually normative.