In my late teens, I was held up at knife point.
At first when he asked for all the money in the cash register, I said "Oh yah, that's funny". I thought he was joking. He demanded again, and I laughed again, and I gave the same response.
His third request however included showing me the 10" knife that he pulled out of his sleeve. I was not at all scared, I just thought "Oh, OK, I'm being held up. I should make note of what he looks like and what he's wearing, and take note of his height against
the height markers as he walks out the door".
I gave him the money, and then he asked me to go into the back of the store. I simply said "No". He then walked toward the end of the counter that was between me and him. I thought he was going
to try to grab me and force me into the back room, but he ended up just reaching out to cut the phone cord and then ran out the store. In every moment of this experience, I was completely calm, and even after, I had no fearful thinking about it, other than
a brief thought that being taken into the back room would not have been a good thing.