I've only got a very limited range of emotions. (High-functioning autism). So I simply don't have vast amounts of either happiness or unhappiness. (I've no concept of grief, for example, but I also can never get to the position of feeling like jumping for joy). I actually regard emotions as pointless, so I try to avoid having them at all (which isn't very hard for me!).
However, within the limited range of my emotions, having 5 cats around the place has definitely taken me towards the upper end, so I suppose you could call me 'happy'.