Whatever the songs about lost love say--forgetting's easy. You can forget things simply by walking through a doorway.
Researchers at the University of Notre Dame did an interesting experiment. They got their subjects to memorize a series of colors and shapes. Then they'd see how many of them they could remember. That's the dependent variable. The independent variable is that before they were asked to recall the colors and shapes, some of subjects walked through a real doorway, some walked through a virtual doorway and others didn't walk through a doorway at all. Those subjects who walked through a doorway--either real or virtual--had much worse memories than those subjects who stayed put.
The moral of this fact? DESTROY ALL DOORS.
Fact found on Dr. Karl's Great Moments In Science.