Yoga Sutras 4.25
Patanjali, explained by Swami Vivekananda
तदा विवेकनिम्नं कैवल्यप्राग्भावं चित्तम् ॥
tadā vivekanimnaṃ kaivalyaprāgbhāvaṃ cittam
Then, bent on discriminating, the mind attains the previous state of Kaivalya (isolation).
In plain words: Then the mind, turned toward clear seeing, moves toward Kaivalya, which means freedom or standing alone as the pure Self. The teacher adds that with long practice the veil drops and fear ends.
Swami Vivekananda explains
Thus the practice of Yoga leads to discriminating power, to clearness of vision. The veil drops from the eyes, and we see things as they are. We find that nature is a compound, and is showing the panorama for the Purusha, who is the witness; that nature is not the Lord, that all the combinations of nature are simply for the sake of showing these phenomena to the Purusha, the enthroned king within. When discrimination comes by long practice, fear ceases, and the mind attains isolation.