Become more and more innocent, less knowledgeable and more childlike. Take life as fun - because that's precisely what it is!
A serious person can never be innocent, and one who is innocent can never be serious.
If you find a saint who has no sense of humour, then he is not a saint at all. Impossible. His very seriousness says that he has not achieved. Once you have some inner experiences of your own you become very playful, you become very innocent, childlike.