My metaphorical understanding is as follows: Tom (Conscious) and Dick (unconscious) are in a locked room looking at each other. The lights (cathexis) are turned off and Dick moves without sound to another location in the room. In Tom's mind's eye, he pictures Dick exactly where he was before the lights went out. However, the darkness (broken cathexis) has broken the visual bond so they are no longer visually in touch with each other even though they are still in the same room.
This is just one example of the insight that I gained from reading this book. This book is helping me understand and use NLP and hipnotherapy techniques with greater effectiveness.