It's easier to live in harmony when you know yourself and the person you're living with. Not "know" as in, "Why, hi, I'm Bob, glad to know you, want to live with me?" But more like "know" as in you've spent quality time and effort to figure out how you and your partner think (process information) and react to a wide range of (often unobvious) challenges.
Most of this book offers things to think/talk about that may not have occurred to you. That's because we're usually blind to the ways we've been brought up; we don't often think about how we think and we don't often challenge our own beliefs. Friction arises from these areas of invisibility. Once the veil is lifted, and once you realize how you've been controlled and influenced by your personal upbringing, you're in the enviable position of being empowered to choose to stay that way or to change. All change will affect your relationship. These changes, themselves, may well improve your relationship(s) to the point that more heavy-duty "problem-solving" techniques are unneeded.
In my view, it's so important for you try on. In my view, it's so important for you try on your new self (and your new understanding of your partner) that the serious discussion of actual issue-solving strategies doesn't even begin until Chapter Seven; if your concerns and upsets hang on to you through Chapter Six, we throw the kitchen sink at them in the final two chapters.