Lack of sleep, hunger or overeating, being criticized by the owner for doing something wrong, being frightened, being in a strange environment, having the owner leave, etc. will all cause the dog to be depressed and stay quietly in the corner. At this time, people around you can feed the dog some food appropriately, take the dog out to play, or gently pet it to ease the dog's mood. Dogs are emotional animals and can feel the emotions around them. If the owner is sad, the dog will also be unhappy.