I was chopped at Culdrose after failing the rotary conversion on the Hiller 12E.
Like many before and since, I had been struggling for a while and what was once thoroughly enjoyable was becoming a daily dread; the feeling of icy water reaching one's neck and not knowing how to swim. 'Failure in Airwork' was the term used, but the written comments of the instructor still ring: "xxxxx constantly yawns during my flight briefings. I didn't realise I was so boring" .
It was many years later that I learned that yawning is a reaction to stress. Maybe they teach instructors to recognise this sort of thing now.