The Conversation Can Change Before Either of You Realizes It.
Maybe it started with money. A chore. A tone of voice. A text message. Something involving the kids. The original issue may be real—but at some point, you're no longer only talking about the original issue.
One person is still focused on the original issue.
The interaction begins becoming part of the problem.
Now you're arguing about what happened during the argument.
The conversation ends. The underlying pattern may not.
