While it is true that you learn your spouse that well, it will be long before that when you realize if don't like them. However when you don't communicate, you

While it is true that you learn your spouse that well, it will be long before that when you realize if don't like them. However when you don't communicate, your lives get out of sync. At some point this has gone on long enough, the changes we go through (called life) cause people to become strangers again. It's like two inertial systems. They drift, differently, over time and this difference accumulates. Communication between the two inertial units can synchronize them. Or a trusted third party (GPS) can give them both a course correction.