I have been in your situation, I am a teacher myself, once a student was very angry with me because she failed the subject I teach, she wrote me that I had been unfair with her and she was much too good for me. She even went with the head of my department and compleined about me saying that I choose whom to fail and I change the marks of her classmates. I just stick to the truth and tried not to think about what was not under my control When I was asked to talk to the head of the deparment I was less nervous that I expected, just holding myself to the facts and not to what could happened or what others thought about me. Do that, just think about what happened and not about the past or your fears or feelings. Good luck!