Two core principles: Practice and non-attachment are the two core principles on which the entire system of Yoga rests. It is through the cultivation of these two that the other practices evolve, by which mastery over the mind field occurs, and allows the realization of the true Self.
Abhyasa/Practice: Abhyasa means having an attitude of persistent effort to attain and maintain a state of stable tranquility. To become well established, this needs to be done for a long time, without a break. From this stance the deeper practice continues to unfold, going ever deeper towards the direct experience of the eternal core of our being.
Vairagya/Non-attachment: The essential companion is non-attachment, learning to let go of the many attachments, aversions, fears, and false identities that are clouding the true Self.
They work together: Practice leads you in the right direction, while non-attachment allows you to continue the inner journey without getting sidetracked into the pains and pleasures along the way.
Supreme Non-attachment: Gradually, non-attachment expands to the depth of the subtlest building blocks (gunas) of ourselves and the universe, which is called paravairagya, supreme non-attachment. Eventually the three gunas resolve back into their cause during deep meditation, leading to final liberation.
Excerpt from swamij.com Article Yoga Sutras 1.12-1.16: Practice and Non-Attachment