Does your character have a fear so strong that it literally paralyzes her/him?
I learned that I do, when I found myself for the second time within a month curled up and crying at the mere thought of the thing I fear.
What is your character’s strongest fear? What makes it so strong (are there several elements at work here)? When does your character become cognizant of it? What happens when the feared event occurs/doesn’t occur? Where does your character’s courage to continue to function in the face of her/his fear come from?