What Hit Points Represent: Hit points mean two things in the game world: the ability to take physical punishment and keep going, and the ability to turn a serious blow into a less serious one.
-Pathfinder RPG Core Rulebook
When using this variant rule, lost hit points recovers naturally at a much faster rate. This system also introduces a special type of damage - Injuries - which recovers naturally at a slower rate.
By default, damage taken in combat represents tiring parries and dodges, deteriorating protective equipment, strained morale and dumb luck; a creature's various defenses get worn down after many intercepted attacks, and this leaves them vulnerable to a more devastating hit.
Injury damage is just like regular damage except that it represents connecting hits that physically injure the target, resulting in serious cuts, broken bones and burned flesh.
An Injury results from:
• Any confirmed critical hit.
• Any failed saving throw.
• Any "final blow" that grants the dying condition (fewer than zero HP remaining).
When a creature is injured, subtract the damage amount from its current Hit Points as you would normally, but note the amount of damage that was dealt by that attack separately as an injury.
Mundane or magical treatment cures Injuries and normal HP at the same rate, but injuries are always healed first. Non-lethal attacks never cause injuries (although a confirmed critical may still double the amount of nonlethal damage received). Objects always suffer injuries regardless of the attack, as well as any entity that lacks a natural ability to recover lost hit points.
Rest replenishes both normal Hit Points and Injuries simultaneously, albeit at different rates;
• Regular Hit Points heal naturally at the rate of 1 hit point per hour per character level (or whatever campaign’s rules for healing non-lethal damage).
• Injuries heal at a rate of 1 hit point per day (or whatever campaign’s rules for healing lethal damage).