Like dark clouds in an otherwise clear sky, they will eventually
   blow away. It's the process of -allowing- the tme to pass when
   feeling empty and/or weighed down that can be dreadful. It WILL
   pass. (then you'll feel better --- and then, you'll feel worse
   -- and then better again -- part of the cycle of things which
   can be so darned annoying. I usually check my biorythm when I
   feel like that or blame my biochemistry and take a B-complex
   vitamin. It helps a tad. "