Vaalingrade
Legend
Let's start with Inspiration. It can come from either an in-universe or meta source, but when Inspiration is used is entirely player-side with the option for the player to flavor it as being in-universe.What "stuff" exists in a narrative space and shouldn't be diagetic?
Or Action Surge; if we're making real life comparisons, you can't turn your adrenaline on or off; action surges are the player deciding when it kicks in or narratively, decides this is the moment the theme music kicks in and their character gets to act extra badass.
Like I said before: the game isn't trying to simulate reality, it's trying to simulate a fantasy story and filling in author fiat with handles for the players to push and pull to control elements of the narrative.
As this pertains to healing, well, I'd be lying if I said I'd hate to say it, but hit points are a narrative element. They're a measure of how long a character can last in a dangerous situation. That's why a dagger that would straight merc a real person only do a d4 impossible to kill a PC damage and why instant kill powers ignore them.
There is a community-created justification for them--which was never in the actual game, but we've moved past that--in the form of meat points, but ultimately nothing keeps someone from justifying them differently for their character concept.
For example, unless he's played by Lazenby or Craig , James Bond can by put through the ringer, but never bleeds, only has to straighten his cufflinks right up until he loses and gets knocked out. Contrarywise, John Mclean visibly degrades throughout the adventure, bleeding from places that never even got touched.