But in 4e, I regard hit points as roughly a victory/momentum marker. The lower the character's hit points, the more the momentum of battle is turning against him/her. Hence a rousing word from a battle captain, or a word of blessing from a cleric, can re-invigorate the character and restore momentum, turning the tide. I assume that the PC's emotional and cognitive state corresponds to that of the player - for instance, if the player knows that his/her PC is low on hit points but is relaxed because s/he can see that his/her PC is in no danger because the other PCs have the situation under control, then I take it for granted that that player's PC is feelingthe same thing: s/he is in no real position to contribute to the fight, but is content to stand by while his/her allies clean things up.
Conversely, when a PC is bloodied and is confronted by multiple enemies any one of whom could render him/her unconscious with a hit and a lucky damage roll, I assume the PC's state of mind corresponds to that of the player: anxiety, a degree of desperation, a readiness to give it all and do whatever it takes to survive (mechanically, that correlates to daily powers, and at the metagame level to scouring the sheet for possible life-saving combos, etc), looking around to see if fellow PCs can provide any aid or reassurance, etc.
Hence my comment, either upthread or on another of these healing threads, that 4e healing works the same way in the metagame as in the fiction: it provides comfort and reassurance both to the PC and to the player.