This data pack adds in a sanity bar. It will not be applied or active in creative. Your sanity bar range is 0-24000. It takes 20 minutes(one full day-night cycle) for you to go completely insane. To cure insanity you must craft a dandelion of sanity. It is 2 spider eyes, 2 rotten flesh, 2 bones, 2 gunpowder, and an ender pearl. The recipe is shapeless and when crafted it resets your sanity bar. Your sanity bar is displayed in your action bar. Here are the effects of going insane:

When your bar reaches 18,000: You gain speed 1 and hunger 2
When your bar reaches 22,000: Harmless explosions in the sky appear across your screen and give you weakness 2. They only appear for you
When your bar reaches 24,000: You gain a wither effect and slowly die.

If you want to remove all your sanity using a command do:
/function insane:givemask
If you want to give yourself 2,000 insanity using a command do(Warning: If you go to high using /function insane:giveinsanity, you will have to do /kill @s to reset/):
/function insane:giveinsanity

Here is a video if you are still confused:
https://youtu.be/VRVNQEqAHl0