Happiness needs no cause. It is your simple nature, you are intrinsically happy. No cause, no purpose, no goal is needed. Life is in itself enough. It needs nothing else to complete it. It is complete! It is entire! It is already what it has to be. So there is no purpose in existence and no goal in existence. Existence is a sheer dance.
It is your right to be happy and yet you create your own un-happiness by wanting things. Wanting is the source of per-petual restlessness. If you do not get the thing you wanted, you are disappointed. And if you get, you want more and more of it and become unhappy.
There is a problem with your concept of enjoyment. You need an object to enjoy, and then you depend on that object. You search for an object, and you work hard to obtain that object; then you are disappointed, because no object has the capacity to give you enjoyment.