I think happiness is related to age.
When we were young, we didn』t know what happiness is.
Children don』t care about whether they live in happiness or not. When they are playing they can be happy. But I think it is only fun but not happiness. And an hour later, they will forget the feeling of fun. Maybe they will be caught into other things. These things make them feel bad, and then they feel unhappy. Another hour later, they forget it. I think the one who is young can』t recognize what is happiness. They are happy because they are in the mood.
Adults are different. They enjoy the memory. What they care about is much more meaningful. When they are unhappy they are worried about something. When they are successful they feel happiness. And what is most important, they hold the memory in their mind and enjoy them.