How does a person know that they are afflicted by the evil eye?

We have not come across anything definitive regarding this matter. However, some scholars have mentioned that the one who casts the evil eye might do so unintentionally, and may even afflict himself. As Ibn al-Qayyim said in "Al-Bada'i'": "The one who casts the evil eye may afflict someone he does not envy, be it an inanimate object, an animal, plants, or wealth, and sometimes his own eye may afflict himself."