Weel for me the best trading psychology drill is to improve and learn on the go. The more you trade thebetter you feel. The more experienced you get the more self-confidence you have. It's all about your skills. Of course its hard to control your emotions but being an expert will definitely help to see if a small loss will lead to a large one or not and if its worth feeling bad or not.
I completely agree. The more you trade, the more experience you gain, the more you get used to the stress that comes with trading. I don't think most people ever become completely numb to it, but one can definitely learn how to manage their stress levels over time and as they become more experienced.