Fear is difficult to overcome. You are constantly thinking about what could happen or what will happen, that it doesn't matter the width of a cliff ledge or school corridor; it will always be easier to walk a school corridor. Ask yourself this: Would I rather walk on the edge of a cliff, where I could fall, or along a school corridor, where I could bump into walls? The answer should be simple. A school corridor, no der. Now ask yourself why. I would say, "Well, bumping into a wall is a lot better than falling off a cliff!!"
Because of your fear that you just might fall off the cliff makes it a lot harder to walk along a cliff ledge than a school corridor, no matter the width.