I just keep it simple. HP is an abstraction, a simplification we make to have a game that's easy to play. One which has been adopted by many other games because even though it's not a good system it's simple, easy and for most people works reasonably well.
I can't even imagine how you'd go about modeling anything at all realistic to replace hit points. We can break it up into two categories where one is sort-of-damage and another is actual-real-damage, but does that really make sense? One guy who relies on dodging out of the way, rolling with blows or deflecting blows has exactly the same numbers and structures as that big hulk of a guy that gets punched in the stomach and doesn't even flinch? One is relying on talent and luck to avoid physical damage, the other just takes it because that's just how tough they are. Whether either option makes total sense in the real world, they are common tropes in popular fiction. Think of every time the protagonist goes up to "the big guy" and punches them and looks surprised when big guy only grins. The protagonist still wins the fight in the end of course because they're the heroes of the story.
In most fiction, the combatants are effectively going full blast until one drops. Often the protagonist almost goes down until they get a second wind because they think of how much they love the fluffy bunnies the opponent is going to slaughter if they lose and then they hop up to deliver the final blows. Even when someone was knocked out they hop up, stagger for a moment and then are good to go.
D&D is not a reality simulator. Like almost all games that involve combat, it's a fiction simulator.