Forget politics and being tired. You said directly to someone exactly what you should not have said and cannot stop thinking about how really stupid that was.

Or you can evaluate the conversation and/or situation and ask yourself “what was I thinking and why oh why did I say that”? It is reasonable to inquire further to see if you really are that horrible person you now consider yourself to be.

No one, ever, left this world without doing something completely stupid and regretted it. You can apologize. You can acknowledge your dumbness. You can forgive you and them. And you can learn how you need to feel and be in order to not create this kind of situation ever again.