Adi Sankaracharya’s book "Sata Sloki"
The essential pre-requisite for the dawn of Self-knowledge is dispassion.
This is of two kinds according to Sage Patanjali's Yoga sutras, namely, inferior dispassion and superior dispassion.
The former arises as a result of the realization that attachment to one's house, friends, son, possessions and the like culminates only in sorrow.
A person who has realized that the notions of 'I'-ness in the body (identification of oneself with the body) and 'mine'-ness in persons and things connected with him are the real cause of all sorrow does not seek to attain happiness from external objects which would only bring sorrow.
The second type of dispassion arises from discrimination between what is eternal, namdely the Atman and what is perishable, namely the body-mind complex.
When this superior dispassion arises, all worldly objects and pleasures become as revolting as vomit.