Generally speaking in my games:
1.) Hit Points are not health. When you lose hit points, you're not being wounded. Hit points are your toughness. When that dragon breath covers you, you shield yourself behind your shield, take advantage of a crack in the floor, aim for a gap in the fire, etc... but it diminishes your capability to find those heroic ways to avoid that major wound. When you run out of hit points - that is the blow that connects and takes you down. The rest of the time you explain the attack away as something that doesn't really connect, although it can often deal superficial cuts, bruises, or exposure damage. Dodging that fire may still leave you with burn scars.
2.) When players have an in story reason to try to attack a specific location or thing, such as attempt to disarm an enemy by attacking their weapon: I allow them to try as an action, but if they do not have a class ability to support it, they are told the odds are slim because this is not something they do well. When they need a 20 on the die and have disadvantage ... Well, it is hard enough that most people will not attempt it. For example, attempting to disarm someone by attacking their hand when you have no ability to do so has a DC/AC equal to 15 + (double their attack bonus) and you have disadvantage. Disarming a CR 3 Knight has a DC/AC of 15 + (2 X 5) = 25. You must roll a 25 attack roll with disadvantage to do it, and you deal no damage if you miss.
You might notice that this can be trivially easy with a really buffed attack. For example, when a War Cleric uses Guided Strike / War God's Blessing on a Blessed 'Archer' using a +2 Bow with the Archery fighting style who is a Hobgobling with Divine Soul Abilities, a 20 dex and +4 proficiency bonus; they will be rolling (1d20 disad - which could be offset by the attacker being invisible or hidden)) + 23 + 1d4 - and if they miss they can gain 2d4 + 5 more. That would allow them - on a 2 after disadvantage - to disarm something with a +11 attack bonus 91% of the time... and that is ok because they are using a lot of their combined abilities to get there. There is a decent chance they could disarm Archdevils with a +16 attack bonus (~25%) - and I'm ok with that as it is heroic.
3.) Some of these things make little sense at first blush. However, if you think 'movie toughness', it makes more sense. When you have a sharpshooter that can hit a cooper coin from 1200 feet, there is an unaware target, and there are no magical protections in place, why can't that sharpshooter put an arrow through an eye and just kill pretty much anything large or smaller? In my games, it is because high hit points reflect that natural toughness ... and part of that toughness that you see in a protagnost or antagonist is that sixth sense that allows them to realize danger at the last moment and avoid that killing blow. If the blow does not reduce them to 0 hp, that little sixth sense was enough to save them from a killing blow when they dodge and the arrow grazez their skull instead of going through the eye.
