Success by affirmation

Our affirmation succeeds best when it is specific and when it does not produce a mental conflict or argument..The  dominant idea or belief is always accepted by the subconscious mind...

Endless desires

Your desire to walk the length of the plank would come into conflict with your imagination.You  would imagine yourself topping off the plank and falling a long way to the ground..The more effort you put into conquering the imagination, the greater strength is given to the dominant idea of falling..