Morning sadness

For some reason I can't even begin to explain, I've been very sad when I wake-up lately. Sometimes I can recall my dreams before they disappear into my sub-consciousness, but they aren't sad dreams. If anything, they are actually kind of comical. And yet, the sadness persists. I just don't understand why I am feeling this way. Of course there are some pretty big events on the horizon and a lot of doubt and insecurity in my life, but shouldn't I awake refreshed and positive? Shouldn't I be happy it's a new day?

If so, why am I so sad?