Happiness is a state. There are many things that are just states. There are many mind states espiecially in meditation. Once you see through them understanding will come.
The mind has a way of making sense of things by allowing us to see things in a way that we would understand. It shields us from seeing the real thing until we are ready to see and understand and accept.
Happiness is a state and we can be happy whenever we choose to be in that state. When we need it.
In a way it is as real as we want it to be.
If you make happiness your goal then you will get it but it is only a state. It does not last. Or give any real satisfaction as that is not what it is ment to do.