We hear that couples fight a lot for typical reasons: finances, parenting, housework, family, and sex. It makes sense. When you're in a long-term relationship, you have to decide how to combine two styles of living. Every person has their own associations built up, and those associations aren't always the same as another person's associations. If you come from a background of more luxury, you aren't going to have the same associations about money as someone who came from a background of financial struggle. It makes sense that you would butt heads over those things, especially when building a life with another person.
However, when you think about how all emotions are either love based or fear based, it adds another layer. Couples fight for the same reason anyone fights; it's just magnified by the intimacy and proximity of the relationship. Fighting can sometimes be a subconscious response to protect yourself triggered from fear. A reason couple's might fight over finances is because someone might be afraid of not having enough. They might fight over parenting because they're afraid of making a mistake and scarring their child for life. They might fight over housework because one of them might be afraid of not being recognized. They might fight over the in-laws because they're afraid that by rejecting where they come from, the person they love is rejecting them. They might fight over sex because they might be afraid of waning intimacy and losing the relationship.
In any case, when a couple fights it's because they're afraid of not being loved or seen by the person they're with. The best way to manage a fear based reaction is to turn it into a love based reaction. That doesn't mean denying the fear-based reaction, or not validating those feelings. Before you fight, the best thing to do is sit with the feeling that sparks the tension. Emotional tension is a red flag that some kind of fear has been sparked. Determine whether that feeling is love or fear-based. Is the fear based in reality? (Meaning, if you're fighting over finances because you're afraid of not having enough, do you in fact not have enough?) If the answer is no, you have some direction for your personal growth. If the answer if yes, then you have some direction of what needs to be addressed in the conversation with your partner. Taking the time to do this before a fight will help you choose your battles, fight with a new perspective, and have a discussion with the goal of finding a solution.