What does the word stand for actually? Happiness is from happy, which probably has to do with happen. Happening is something that is going on, in the present.
Like the happening of leaves on a beech tree. One thing I took a interest in this spring. I observed the proces leaflets coming to be and noted that there was no boundary. While the actual unfolding of the leaf happened in a very short span, like a week or so, it wasn't just this instance. It happened over a long time and most of the time the result of green fresh leaves were invisible.
I could observe the beginnings of leaflets in winter already and while the proces happened very slow that time, it did however come to be over time.
So with regards to happiness, it's happening right now but isn't always clearly visible. In winter the leaflets were a sad bunch on empty twigs in the cold winds with gloomy skies. But... they nevertheless became green leaves and are now quite happy I suppose.
Anyway what I mean is that happiness isn't something you can determine as this is it and this isn't. Like the transition from sadness to happiness is gradual and when sad contains a seed of a happiness that comes to be and vice versa.