Defn of Happy and Unhappy

Once upon a time, I read a defn about happiness. "When you have nothing unhappy happening at the moment, you are happy." - for one second, I said, "No way." it can't be, then gradually, I realise, it's true. When nothing worries you, you are happy. Whenever you are not happy, it's because something is botheirng you.

Now, let me trying to reverse this, see if it works. "When you have nothing happy happening at the moment, then you are unhappy." - "No way." Or is it really?