Handling father in law / difficult conversation

I’m planning to implement Brooke’s difficult conversation model later this week when I see my father in law. I get stuck identifying facts. I understand ‘facts are neutral’ but it is tricky to do this in the real-time. I often think my own thoughts are facts (because I think I’m right 🙂 ). Do you have anymore tips on how to identify facts esp during the pressure of a difficult conversation?