Sleep and Rest
Characters ought to get a full night’s sleep every night. Some characters require sleep in order to regain enough energy to prepare spells the next day.
In order to gain any benefits from sleep, the following conditions must be maintained throughout the entire period:
before sleeping, make sure to cross off appropriate food for the day (1 lb if sedentary, 2 if working or traveling, 3 if there was any combat)
minimum duration of 6 hours
must not wear armor
must be appropriately protected from the elements
Not Getting Enough Sleep
If a character can’t fulfill the above conditions for one night, they cannot refresh any spells, but otherwise are unaffected.
After a second night without good sleep, they begin to suffer damage at the beginning of the day, representing fatigue, lack of energy, the body’s inability to fully repair itself, and so on. This damage is 1 point on the second day without good sleep, 2 points the next day, 3 points, 5 points, 8 points and so on.
A day’s rest (below) will reset the “not enough sleep” count of days, and will also remove that day’s damage from inadequate sleep, if any.
Resting refers to laying down and performing very little activity in order to allow the natural healing process to take its course.
A character who takes an entire 24 hours to rest regains HP equal to their level or Hit Dice, whichever is greater, plus their Constitution bonus, if positive.
In addition to the above conditions regarding ordinary sleep, the character must also maintain the following conditions in order to regain HP from rest:
walk 400 feet or less throughout the day
neither prepare nor cast any spells (with the exception of healing spells, which may be cast, but not prepared)