It's the elves

After you have lived in your new house for four or five years, elves will come and move all of the electrical switches to the opposite side of the door. You will be tempted to think that this is just you slowly losing your mind, that the fact you have started instinctively swatting at the wall to the right of the door when the light switch has clearly always been on the left side of the door is a sign of some new mental degeneration on your part. But it is not. It is the elves