Cas's hands are already soaked with his own blood from trying to stem the bleed. He can't help but think bitterly that if he still had his Grace he could heal himself in a second. He could heal himself, wipe out any threat in a ten mile radius and have them back at camp within seconds. But those days are long gone. He's as mortal as any one else, and the bleeding isn't stopping.
It could've been worse, he tells himself. He could've been turned. At least this way he dies human - or as close to human as a fallen angel cut off from Heaven can be.
"You know what they say... It's better to burn out than to fade away." At least he'd made some difference in his time with the camp, right?