They Can Be Pleasingly Controllable
In your daydreams, would you rather plan or reflect? To drift to the future (how should I ask for a raise?), move your body forward; to think about the past (lost loves, etc.), move backward. This works subconsciously, found a University of Aberdeen experiment, because space and time are linked in the mind. When volunteers were instructed to watch a star-field animation screensaver (like this one) spiral inwards (an illusion of backward motion), they daydreamed of past events, and when it flowed in the opposite direction, they thought about things that might happen in the future. Self-experiment by derailing your mind on a bus or subway (your choice, of course, of a forward- or backward-facing seat).