If you're feeling sad, gloomy, blue, low, grim, depressed, or melancholy, you probably don't care if there could possibly any more synonyms for the way you feel. Rest assured that there are, and one of them is downcast.
Downcast most frequently describes a person's mood: downhearted, down in the mouth, down in the dumps, just plain old down. It can also refer to the direction in which something is pointed — down. Your eyes, for instance, gazing downward, are downcast. And many times when your eyes are looking that way, it's because you're feeling that way.