Grow back your spleen in 24 hours!

Heal back all your hit points in one night's sleep? I don't think so. Modding the healing rules and saying "sod it" in the end.

Want to know the real rule? The actual healing rule? The rule that'll drive my campaign from now on? Skip right to the end. Of course you'll miss out on the soul searching that got me there, but if you're all tl;dr, go right ahead.

Just a flesh wound.

For those not afraid of reading, consider this likely scenario.

Questing has happened. The prince is safely locked into his iron mask again, occult megafauna have been scrapped for parts, and your heroes are back home. Minus half their teeth, 75% of skin, a spleen and a couple of fingers. Are they down for the count? Are they fuck! In 5E, a good night's sleep is enough to cure all your hit points.

This, let us say, pops my rosy little bubble of disbelief.

Before you hordes of commenters cry out that Hit Points Are Not Getting Hit Points, I know, I know. They represent all the effort you make to avoid the worst of a blow, etc. I just think that even a fit adventurer would be hard pressed to exhaust themselves on a daily basis and recuperate in a long rest. I happen to like 5e's short/long rest mechanic but I want to mod it a bit.

Standard rules for a short & long rest

This being D&D, everything's connected to everything. Resting doesn't only get you back hit points, but also use of abilities such as rage or spells. I'm not about to overhaul the entire game here, so let's see what we can play with. Here's the rules-as-written:

Short rest, 1 hour:

"A character can spend one or more Hit Dice at the end of a short rest. Maximum number of Hit Dice is equal to the character’s level. For each Hit Die spent in this way, the player rolls the die and adds the character’s Constitution modifier to it. The character regains hit points equal to the total." (So a wizard3 with Con 12 can roll up to 3x 1d6+1 before he's out of hit dice).

Long rest, 8 hours:

"At the end of a long rest, a character regains all lost hit points. The character also regains spent Hit Dice, up to a number of dice equal to half of the character’s total number of them (minimum of one die)."

Summary: he'll feel better after a nap.

Solution one: quarter him!

Let's try to mend this quickly and say that a character regains only 1/5th of all lost hit points during a long rest. Does that sound better? On the surface, that sure slows your healing, but in effect, it still only takes two days of not getting murderified to regain all your hit points. Day one, you heal 1/5th hp, use all your hit dice and regain anywhere up to full hp from those, and on the second day you spend some more hit dice to heal up the rest. Bob the Barbarian feels right as rain, two days after being used as a dragon's chew toy.

No, not like...nevermind, nothing a good night's sleep won't fix.

Solution two: short rest, long rest, bed rest

New idea: short rest stays as-is. Long rest refreshes use of powers and 1/2 of your hit dice as usual; no free healing. I'll add the new category of bed rest, which is a lame-ass title but will do for now. A period of bed rest lasts for a week and gets you back all your hit points, hit dice and expended powers.

Still begs the question: why would you ever need a bed rest? Two days of short/long resting will get you back all that anyway.

Extra ingredient to solution two: exhaustion

After this, I need a vacation.

What's to stop a party from pressing on day after adventuring day? They'll be good for hit points and powers anyway. So let's tack on the exhaustion condition from the PHB appendix. Adventurers can soldier on for a number of hard working adventuring days equal to their Con-bonus+Proficiency bonus. After that, they get one level of exhaustion per extra working day. And of course this doesn't go away to the tune of 1 exhaustion level per long rest; you need bed rest for that.

Five days to remove one level of exhaustion? Maybe that's a bit much. I could fiddle around with the length of a bed rest, or say that you just need one full day of resting to remove one level of exhaustion. Here is the rule on exhaustion, by the way; a nice, clean piece of work!

Exhaustion is measured in six levels. An effect can give a creature one or more levels of exhaustion, as specified in the effect’s description. If an already exhausted creature suffers another effect that causes exhaustion, its current level of exhaustion increases by the amount specified in the effect’s description. A creature suffers the effect of its current level of exhaustion as well as all lower levels.

Level / Effect
1 Disadvantage on ability checks
2 Speed halved
3 Disadvantage on attack rolls and saving throws
4 Hit point maximum halved
5 Speed reduced to 0
6 Death

Final verdict: hell with this

To be honest, if I have to choose between realism and awesome-up-your-players, my money is on the bunch of murderhobos that kill Bullette with their teeth and overclocked cantrips. Realism can go cry in the corner.

Sure, I'll remove "heal all hit points after a long rest", I'll use the exhaustion rule when I remember and feel like it, but tracking how many working days the players have gone without a proper bed rest feels like too much hassle. Punch clock heroism isn't my style; ideally my players get to feel that their characters are bad-asses, not a bunch of athletes who have to monitor every aspect of their physical well-being with a careful training regimen. Thus we end up with this loose-fast rule:

Short rest: heal by expending hit dice; regain use of some abilities
Long rest: recover 1/2 of expended hit dice; regain use of some abilities
Pushing it: eat a level of exhaustion for when you've been fighting hard day after day after day. Take a day or two to recuperate and have at it again. The Halfling Horde doesn't lounge in the spa getting its nails did, neither should you.

Fine, have a quiet day at the local inn.