Joshua is the Christ in you, your own imagination, the same figure as Jesus, and he moves the people to make ready for a crossing. The people are your own thoughts, and the food they prepare is the mental diet you feed on, the inner conversation and images you carry as you approach the change. Three days is a short, steady stretch of holding that diet faithfully, long enough for an assumption to firm into fact.
Jordan is the boundary between the state you are in and the state you desire, and to pass over is to move inwardly from one to the other. The land is any condition you can mentally stand in and feel as real; wherever you can occupy in imagination is already given to you. Whatever state a person can inwardly enter and hold becomes his own. Feed on the wish as fulfilled for three quiet days, cross over in feeling, and the ground you stood on within becomes the ground you live on.