Happiness?

  What exactly is happiness?  I always used to believe that happiness was being happy all the time, but now I don't believe that's possible.  There is always something to bring you down.  I suppose happiness is relative.  If you spend every day of your life wanting to die because you're so depressed you feel you can't go on, then the day you wake up and don't wish you had died in your sleep must be a like a kind of happiness. 
  Bob is back in work on monday.  I'm dreading it.  I've spent the last fortnight actually feling useful for a change.  Bob makes me nervous, and he makes me feel useless and worthless and pathetic.  He has this way of making me feel about 6 years old, like I used to feel when I was in primary school and could never do anything right.  He makes me feel like an idiot, like my opinions are not worth anything, like I'm getting in the way.  I feel like that anyway at the moment, I can't seem to do anything right, I'm upsetting people all the time, I feel like I'm useless, a waste of space, a little bit pointless. It will be worse when the boss gets back, and then Joan is going on holiday too in a week or so.  Joan sticks up for me, she's like my back up.  She has confidence in my abilities, I think she's the only one that does at the moment.  I don't know what's wrong with me, I was happy not so long ago, this evil mood has dropped on me like a stone, suddenly with no warning.