Injuries to the soul usually took a long time to heal, and that was for the lucky ones which even then, wasn't usually achieved through natural recovery. Most injuries to the soul, if not all, required an external impetus, such as a soul-related art capable of aiding the healing process, which would also require the right environment to be effective. If not a soul art, then one would need the hands of a highly skilled healer, or a precious treasure renowned for treating soul-related maladies.
Whether it was a soul-related art, the right environment, a healer, or a rare treasure, all of these options shared one thing in common: quality and rarity.
Take soul arts for example. Any technique with genuine soul-healing properties was at least blue grade. As for the environment, its quality had to be on par with, or greater than what was created by a lesser dragon vein.
