Have you ever had miracles happen?

Have you ever had miracles happen? By miracles I mean instances where for whatever reason, you were completely fluent and flowed naturally. I've given atleast 3 or 4 oral exams and presentations in school last year, but I stressed for months beforehand. Surprisingly, when the time came to present, I found myself completely fluent while speaking and entered a natural flow state. Now, after a year, I'm back to speech blocks and stuttering, having *completely* forgotten what I did back then, and speaking in class is a real pain. Has anyone experienced anything similar? Do you know what may have caused your sudden fluency?