Soul is the place of human communication with heavens. So, if it is not cared properly, the trait of humanity is gradually taken from human beings and he is considered as animal and among beasts. In this world, human can exceed in evil so far as he can be deprived of the divine mercy and graces. Because such spiritual illnesses bring about one’s deprivation from divine blessings. The Holy Qur'an says in this regard:
وَلَا يُكَلِّمُهُمُ اللَّهُ وَلَا يَنْظُرُ إِلَيْهِمْ يَوْمَ الْقِيَامَةِ وَلَا يُزَكِّيهِمْ
Those who sell their covenant with Allah and their promises for a small price will have no share in the life hereafter. Allah will not speak to them nor will He look at them on the Day of Judgment nor will He purify them. They will face a painful torment. (Al-Imran: 77);
source : erfan.ir