D&D 5E Can mundane classes have a resource which powers abilities?

[Ahnehnois]

But, none of this is actually directly related to HP. Not really. After all, I can lost HP without taking any visible physical effects. Heck, HP can be bypassed in many cases such as magic, poison or various other effects, where I'm dead with full HP.

Well, yes, but that's to be expected. I think it's clear that there's supposed to be some relationship between hit point damage and blood loss. This is most clearly evident in the "death window" rules which appear to be a simulation of hypovolemic shock (and in their non-4e incarnations are oddly "gritty" for D&D). But it's possible to die from causes other than blood loss and even without being injured in any way that would impact your circulatory system at all.

So, I think it's simple to say that death effects just stop your heart without causing any observable wounds. I see a lot of abstraction issues, but no real contradictions.

Why is it okay for my character to jump off a 60 foot cliff, dust himself off and jog back up the cliff to do it again, just because I know that it cannot kill me, but it's not okay to have daily limited critical hits?

The first answer, to go back to [MENTION=6696971]Manbearcat[/MENTION] 's point, is simply preference/playstyle. Getting up after a fall and dusting yourself off is (arguably) cool. Heroic. Fantastical. Running out of some ephemeral reserve of luck and being inexplicably impotent until going through some arbitrary recharge process is (pretty much inarguably) none of those things.

However, it's also the old question of dissociation. In the first case, the outcome is unrealistic, but internally consistent. D&D characters are simply more resilient than real people. The second example lacks the same logic; there's no reason why a character would run out of one particular ability as opposed to experiencing generalized consequences of fatigue or what have you, and that illogic is a non-starter for people who are not used to it.

 

[pemerton]

Some examples I can think of from AD&D: the phantasmal killer spell can deal hp damage; and so can psionic attacks. Not to mention hit point damage caused by illusions when the defender fails to disbelieve. (I think someone already mentioned this upthread, or on another similar thread.)

If a psionic is out of points, then all point loss is suffered as hit point loss.