The reason for this is simple. Sleeping is a yin activity and thus, it needs a yin feature such as the wall - solid and immobile - to act as a support to the bed.
Placing the bed in a yang sector will create an imbalanced qi flow, and this will influence your sleeping behaviour and subsequently your health. If the bed is positioned at an angle where its headboard is against a corner, beware as more problems can be expected. While you may have achieved your objective of tapping a favourable direction, you have at the same time created sha qi that points directly to your head.Windows belong to the yang feature. As such, placing the headboard of the bed against the window can inadvertently create an imbalanced flow of qi to the entire room.
Strong wind can seep through the window and hit your head as you sleep, causing you sleepless nights while also affecting your health. You can solve this problem by using thick curtains, and do ensure that the windows are tightly closed when you are asleep.If your feet are pointing towards the bedroom door, the qi will rush in through it and crash into your bed directly, causing restless nights.