When someone is attacked, one of three things happen.
I think it is good to cause the adrenaline dump that can cause someone to freeze up and become rigid.
I tell my students that we train to be as soft and subtle as possible, so if an attack happens, we may become more tense but, not to the point of freezing and not being able to respond, or be effective.
I don't know if fear is the right word...I'm shooting for an adrenaline dump. Albeit, this could be caused by fear, anxiety, stress or a number of things.
Just my thoughts.