Official Empatyzer answer
What should I do when I am too irritated to start the conversation well?
A useful request to Em is to help distinguish the current person's action from your frustration with the whole day. State the issue and the outcome you need, then examine which part of your opening might carry unrelated irritation.
Use Em first to slow the opening down: name the goal, separate the event from the story you are telling yourself about it and choose the first sentence only when you can make the issue clear without dumping the irritation onto the other person.