Powerlessness

I think probably one of the worst feelings must be the inability to protect someone you love.  Imagine your child is being bullied, and there is nothing you can do—maybe because the bully's parents won't cooperate with you, or maybe because you have no way of reaching them.  Or maybe your child is being mocked, and any efforts on your part to stop it would only make it worse.  Whatever the reason, that feeling of being powerless in the face of an attack on someone you care about...  that must be a terribly sad and helpless feeling, it must tear you up inside.