Long Rest Modifications

Characters can only gain the full benefits of a long rest in designated safe areas (e.g., the Grand Cathedral or a heavily guarded inn). The reasoning behind this is simple: you sleep much better at night knowing that you don’t risk getting ambushed or murdered in your sleep. The mental anguish would cause your sleep to be less restful.

A safe area is any location where the party can genuinely relax without fear of being attacked. As a GM, a simple way to determine whether a location counts as a safe area or not is to ask: “Would the party need to set up a watch for the night?” If the answer is no, then you can count it a safe area. If the answer is yes, then it is not a safe area, and they only get a partial long rest (see below).

Rest Disruption: If a long rest is halted, be it by a combat, ambush, emergency meeting, or otherwise, players only gain the benefits of a partial long rest (see below). If they do not return to complete the long rest immediately after the interruption, they gain the benefits of a short rest only.

Short Rest Modifications

Only the first two short rests after a long rest (not a partial long rest) recharge abilities, like a warlock's Pact Magic or a monk’s ki points. Additional short rests before taking a long rest solely permit hit dice rolls for hit point recovery.

Partial Long Rest

Resting outside of safe zones, meaning anywhere where you’d have to set up watch, offers limited recovery. At the end of a partial long rest, characters:

• Regain one-third of spent Hit Dice instead of one-half.

• Regain the use of abilities that recharge on short rests. However, long
  rest-specific abilities remain depleted.

• Don’t lose levels of exhaustion, but they don’t gain any as a result of not
  taking a long rest.

• Spell Slot Recovery: Spellcasters regain spell slots with a combined level
  equal to half their class level (rounded up). For instance, a 4th-level wizard could regain a 2nd-level slot or two 1st-level slots.

• Regain the option to take one short rest that recharges abilities before they must take a long rest. If they were already able to do so, they can take one additional short rest that recharges abilities (to a maximum of two).