Mental Reserve

Mental Reserve is the overall capacity of how much magic a magic user can possibly use over the course of a Combat encounter before they drop to Mental Exhaustion. Running out of mental reserve causes Mental Energy to be unable to recharge when depleted, which is the mental equivalent of getting "burnt out" and unable to fight anymore.

This reserve can only be replenished by sleeping, and per unit time, is more efficiently restored when the rest is a good night's sleep at a healthy time, on a comfortable bed and in a comfortable, warm position.