Scientifically speaking, mirrors reflect light. When you sleep at night, if there is light outside, it will affect your rest (subconscious).
Classically speaking, the mirror is anti-evil. Facing your own bed, evil spirits are reflected on your own bed. Do you think this is a good idea?
Hehe, if you don't want to move,
Covering up is really a way.
But you can cover it when you sleep, so you don't need it at ordinary times.