Yeah I used to do the fake cheerful thing, which does work and tends to defuse a lot of anxiety in the situation on both sides. But then I got old and tired of it so now I just say things as straight as possible, no smile to sweeten the message.

You reminded me of the a time I took a colleague aside to tell him how to spoke to me during a meeting was definitely not ok. He looked absolutely petrified. I felt bad afterwards, but I had kept my voice very low and monotone (I couldn't raise my voice anyway as we were in an open plan office) but I think the scowl on my face scared him lol.

Love your idea of trying to "be like a jedi". I use mental images like this to help me stay calm as well. :)