The whole saníty thing doesn´t work very well in any of the books, because it is badly explained. So unless you code dive you have no idea what it actually checks.
In book one my character always seem to have lowish sanity, but nothing they do and nothing in the way they are described actually supports that. They don´t seem stressed, not really very affected by the monster attacks, and we have no choice, but to have a social life outside our studies wherever we want to or not, so I really don´t understand why it is so low.
In book two we are canonically stressed, but there is nothing we can do about it. (At least not what we are allowed to. Even when I pick every single I need to sleep option it doesn´t help.). The therapist doesn´t help either. It honestly feels like I am dragging something with the character from book one, but at least I understand it because it is actually described what is causing this, this time.
I must admit that I am a bit worried about book three when it comes to sanity. I fear that I get locked into a bad ending, because of a stat I can´t see.