Hi, I hope it's not.to late to reply, but I would recommend you to read 'the 4 hour workweek' by Timothy Ferriss. It's eaxctly about this: what to do of your free time when you have enough money to sustain your lifestyle.

Also if you can read french, I would recommend 'le bug humain' by Sébastien Bohler. It's an introduction of the inner working of our brain. Basically it says that the only sustainable thing that can both please our lizard brain and do not destroy our planet is learning.

Happy new year :)