Harry Potter and the Prisoner of Azkaban

— Why do they affect me so, Professor? I mean, more than everyone else...
— Dementors are among the foulest creatures that walk this earth. They feed on every good feeling, every happy memory, until a person is left with nothing but his worst experiences. You're not weak, Harry. The Dementors affect you most, because there are true horrors in your past. Horrors your classmates can scarcely imagine. You have nothing to be ashamed of.

- Why do they affect me so, Professor? I mean, more than everyone else...
- Dementors are among the foulest creatures that walk this earth. They feed on every good feeling, every happy memory, until a person is left with nothing but his worst experiences. You're not weak, Harry. The Dementors affect you most, because there are true horrors in your past. Horrors your classmates can scarcely imagine. You have nothing to be ashamed of.