To be sincere is one thing, to be serious is another. A man who loves life is sincere, authentic, but never serious.
Remember, an authentic religious person is not fear-oriented, he is love-oriented. A really authentic religious person becomes religious to enjoy life more, to enjoy it deeply and totally.
A real religious man looks at life as a game: it is not business, it is a game. Hindus call it LEELA, a play; not even a game but a play.
There is a difference between a game and play. Children play, but you even make a game out of play. Then it becomes business-like, then even in playing you are seeking victory, success, gain, profit.
Life is a play. There is nothing to be achieved out of it, it itself is the goal; there is nowhere to reach, it itself is the Ultimate.
It is just like children playing, you cannot ask them: For what are you playing? What is the purpose? They will say: We are simply playing. It is so beautiful! Profit is not their concern, and profit should also not be your concern, but play.
Life is a moment to celebrate, to enjoy. Make it fun, a celebration, and then you will enter the temple.
...if you have lived, lived a life of celebrations, then you can die celebrating - it is fun. When you know that you are not going to die, that something in you is eternal, then the whole of life becomes fun. It is a great cosmic joke and you can play with it.
Osho, Returning to the Source Chapter 10 : So Teng Died Standing On His Head