Trauma has an effect on the subconscious mind and it explains a lot of things we don’t understand on the surface. People are more likely to stay in groups that traumatize them in some way like friends that make mean jokes or organizations that abuse their members behind the scenes. They are also more likely to form closer bonds with people they experience traumatic experiences with. Even in the context of some magical practices, giving blood or self-injurious behaviors are sometimes used to bring manifestations.

The reason for this goes back to survival, and because it draws upon the abilities and The God Of Fear And Hunger. Even animal sacrifice or human sacrifice is traumatic to a person who performs it which would explain why they are such common tropes around the world. You obviously should not do anything to harm yourself or others, but performing tasks you would rather not, eating spicy food, or using trauma to manifest will bring results.