Darkness decends

What is one to do when the darkness comes crashing down?  When your very soul hurts.  When any thought is painful.  When nothing seems good or right.  When there is no hope.  No chance.  When all choices are painful and bad.  When even breathing is too much work.  When you feel betrayed by the world, by God, by the ones you love.  When it feels like there is no way out.  Nothing.  This is what I haven't found in any of the books.