When I was a kid we got to visit paris. While we were there we went up the Eiffel Tower. There is one thing I remember about it very vividly. My mother wanted a picture of us and so she told us to back up. I caught my foot on the grate and fell over backwards. I was a long way from the edge, but even at that age I remembered thinking, this is it, I am going to fall off the Eiffel Tower and die. To this day I am not a big fan of heights.
Most people have had an experience like this something that they can point to and say, this is why.
Today's writing prompt is, take that experience, and make it part of your character, or give them their own Eiffel Tower moment. Have that be the one thing holding them back. Will it be there down fall or will they over come it and be a hero?