When having a difficult conversation about something, you want to plan and planning means answering the following questions:
1. Why do I want to have this conversation? What do I hope to achieve?
2. How do I see things? How does the other person see things?
3. How do I feel about the situation? How might the other person feel?
4. What needs of mine are not being met because of the situation? Or what value that I hold dear is being undermined?
5. Is what I am feeling (the impact) the same as what the other person intended?
6. What was or is my contribution to what happened? How do I see the other persons contribution? (Contribution is much more useful than blame)
7. What part of me could be at stake when I have the conversation? (Identity issues)
8. Could there be conflict in me rather than with the other person?
9. Is a conversation the best way to deal with the situation?
After answering these questions, you should have a clear answer as to whether you will actually proceed with the conversation or not. And if you do go ahead, you will be pretty well prepared to have a conversation that is learning-oriented and human-oriented.
Good luck!