I'm not sure how to do that. But you can recover sanity from sleeping, using anything with Cleansing Water in it or just by going inside the cleansing lake under the lizard's temple.
Aww!, But thanks anyway!
Note that you can temporarily lower your maximum sanity with certain equipment, so be wary of that.
What are the equipments?
I don't remember, I know one of them is a ring.
Thank you anyway!
