First piece of advice. In arguments, look at an issue from all possible angles. Sometimes we defend our own point of view, and we can't find a compromise. Ideally, one should look at the situation from one's perspective, from the other person's perspective, from the perspective of logic, and so on.
You have to take into account as many factors as possible. This way, in reasoning, the person will see that you don't want to argue and ruin the relationship, but really want to find a better option. Such people are appreciated, because they are honest. And vice versa, do not like those people who stand on their own, and do not think about others.
The second tip is honesty. Lying often complicates relationships. One told one person one thing, the other another another, and the meeting of the three of you creates discomfort. There are many examples, but the whole point is that the person lies, understatements, and so on. Maybe he wants to please everyone, doesn't want to offend, and so on.
But all this only complicates the relationship. A perfect example is the American soap operas. There you can often see this line, when a person at the beginning of an episode lies, or tries to hide something, and the whole episode he has tension and misunderstanding with those around him. Honesty is needed in a healthy relationship. And not just with your other half, but with others around you.
The third piece of advice is to know how to say no. After all, many people have problems with this. For example, you were called somewhere, you want to stay home, but you can not say "no. As a result, you get together with good people, but in a bad mood. This ruins the relationship. People think that it was them who spoiled your mood, they take it personally.
There are a lot of examples like that. But the point is the same, it's when a person can't say no. That's why you have to practice. First say no to a little, then to a lot. It is better not to lie, not to make excuses, but to say "no" directly. That is my opinion.