I dislike the way d20 systems tend to give you free hp bonus as you level up. While GLOG does away with the hp bloat the plagues other systems, you still gain hp with level ups. Yes, you are learning, getting more experienced and better. But that's why you gain new abilities with levels, so why would you also get harder and harder to put down in combat when your area of expertise is elsewhere? Fighting classes, who are most definitely justified in getting tougher with experience, already get class-based hp bonuses, so why retain the automatic increase for everyone?
Therefore, your hit points no longer increase from levelling. You have maximum hp equal to your Constitution, plus any class bonuses and such. That makes low Con character very fragile, but then that's to be expected and they can try playing in a way that does not put them in the harm's way.
In the same way as "don't get hit" points are a measure of how well you can take physical punishment without injury, I'd like to have an abstraction of mental health / stress resistance / sanity. This will be your willpower (wp) and will work in pretty much the same way as hp. You will have maximum wp equal to your Wisdom, plus any class bonuses and such.
In addition to psychic damage, I'm thinking about making fear, charm and similar mind-affecting effects deal damage to your wp, straining your psyche until you snap at 0 wp. Rules for stress from dungeon crawling, horror of meeting monsters, madness, insanity and nervous breakdowns will also be required. :)