... a family I know ... bought an acre in the country on which to build a house. For many years, while they lacked the money to build, they visited the site regularly and picnicked on a knoll, the site's most attractive feature. They liked so much to visualize themselves as always there, that when they finally built they put the house on the knoll. But then the knoll was gone. Somehow they had not realized they would destroy it and lose it by supplanting it with themselves.