The having of fun is the result of your consistent and continual movement up the vibrational scale, an energy-based scale. Movement up the vibrational scale occurs every time your attention is given to points of focus that feel slightly better than your previous thought.
The process of having fun while manifesting your desires, such as having fun while thinking about them or while taking actions to fulfill them, is a very powerful process for you to engage in since it allows for you to focus on your desires in a way that makes you feel better and better which will naturally result in the creation of increasingly better feeling experiences that match your desires more precisely.