I had another memory that was false, but proved to be useful. I remembered staying at a local motel in my current condition before moving to this town. I had knowledge of motels and handicap rooms that was useful in making a trip. That memory never happened.
I've let a natural process called pruning handle these memories. The second memory had my father's mother in it. She passed away years earlier. There was no way possible that experience ever occurred. There was no logic in it. It wouldn't be reinforced and would "prune" away. http://www.princeton.edu/main/news/archive/S41/88/27A90/index.xml?section=featured
The jelly and cheese sandwich was different. I had no way of proving or disproving the memory...until I heard my mother. Now that memory, too, can be forgotten.