Yoga Sutras of Patanjali translated by Yogi Kalinath - Chapter 3, Verse 10
Pada 3, Sutra 10
Tasya prashaata-vaahitaa sanskaaraat
The restraint of subconscious impressions brings about an undisturbed flow of calm.
The flow of calm experienced by the Yogi when the subconscious impressions are repetitively restrained are analogous to cognitive absorption. In that state the mind no longer struggles against itself.
The mind is such an unruly servant that it needs Abhyasa (constant practice) and Vairagya (intense detachment) in order to quell its subconscious impressions and hallucination of being a being of substance.