A bad mood is a terrible negotiator. Reschedule the conversation.

In a bad mood everything reads as an attack, your tolerance for a slow answer disappears, and you start working to feel better rather than to get what you wanted. You will say the sharp thing, and the sharp thing becomes what the conversation is about. The position you came in with gets abandoned for free.

When you notice the mood before the conversation, move the conversation. Asking to talk about it tomorrow costs almost nothing and nobody minds. If you are already in it and feel yourself going hot, say you need a minute and take the minute.