Damien was left with only 2-10th of his divine power by the time he finished healing all of them.
It was as valuable to him as oxygen for humans.
He wouldn't be able to stay alive without it, after all. However, he hadn't hesitated to use it for the benefit of others because he knew his breaths were numbered.
The body of a mortal wasn't a good enough vessel to contain or process it.
That's why it is said that divine power isn't something a human should have.
As he had an Earth-grade physique, he was able to forcefully keep it inside of him and use it as he liked forcefully.
If he hadn't contained it inside of himself, it would have rushed out of him. As a result, his body would have exploded.
Though, keeping it inside himself and then processing it and using it as fuel to activate his ability did a lot of irreversible damage to him. It was the type of damage from which he couldn't recover.
