Suffering from the implications of when I was 10?

Dark does tend to make a room appear smaller but in a bedroom it sometimes works. If you like the coziness of a cave like space it would work. if not choose a dark neutral tone like dark grey or a dark tan. go light on dark color though. too much can be too much. maybe an accent wall with a dark color with the other walls in a dark neutral a few grades lighter than the accent wall.