Zhuangzi (say "jwahng-dzuh") wakes up certain he is himself again, and then cannot say which of the two was the dream. He doesn't doubt that a man and a butterfly differ. He doubts he can tell, from inside, which one he is currently being. The version of you rushing through this morning, certain the deadline is a crisis and that stranger's tone was an insult, feels exactly as real as the butterfly felt to itself. Today, when a mood insists it's simply how things are and not a mood at all, treat that insisting as the tell, not the proof.
I, Zhuang Zhou, dreamt that I was a butterfly, a butterfly flying about, feeling that it was enjoying itself. I did not know that it was Zhou. Suddenly I awoke, and was myself again, the veritable Zhou. I did not know whether it had formerly been Zhou dreaming that he was a butterfly, or it was now a butterfly dreaming that it was Zhou. But between Zhou and a butterfly there must be a difference.
Zhuangzi, ch. 2, "The Adjustment of Controversies" (trans. James Legge)