If you need to take some time to cool down first, do so.
It’s best to be direct and specific. You want people to understand what you are trying to say, and not distract them with other topics.
When I [heard/observed/reflected on] your [action/behavior/output], I felt concerned because…
I’d like to understand your perspective and talk about how we can resolve this.
The compliment sandwich can lose the actual message, Zhou dislikes it.
Julie Zhou, The Making of a Manager