Complete mastery over the modifications of the mind is called yoga.
Yoga Sutra 1.2 Recitation
Audio Recitation by D.C. Rao, PhD
Yoga union, balance; harmonious state of mind; bridging the different aspects of life; connecting the individual consciousness with supreme consciousness; the union of the two–the lover and the beloved, the seeker and God, Shiva and Shakti, ida and pingala, the sun and moon, active and passive.
Chitta mind; the repository of thoughts and feelings; that which thinks and feels; the inner instrument for thinking, feeling, perception, and cognition; the instrument that consciousness uses to explore its own manifestation; the leader of the senses; the seat of the spirit.
Vṛtti thought constructs; modifications; that which rotates like a wheel; movement.
Nirodha = ni + rodha
Ni completely; in every respect; from every direction.
Rodha confining; restraining; disciplining; not allowing to roam aimlessly.
In a single, monumental sutra Patanjali has created a thread of understanding that connects all the practices of yoga. It illumines the core of spiritual life.
Meditation and contemplation are powerful tools for training and disciplining the mind.
Attaining mastery over the modifications of the chitta, or mind, is the core of yoga practice. According to the sages, the mind stands between the unmanifest, transcendental reality and the manifrest world. It is that which stands between body and soul.
The mind is like a customs officer: anything this is imported or exported between the soul and body (pure consciousness and the material world) passes through it. The divine within us constantly sends its gifts of love, knowledge, and happiness, and we also offer our love to the divine. But if the customs officer is corrupt, this exchange is disrupted and all communication and exchange of gifts is obstructed. The goal of yoga is to train the mind, discipline it, and remove its corrupting tendencies.
Meditation and contemplation are powerful tools for training and disciplining the mind. Meditation makes the mind one-pointed and vigilant. By practicing meditation we train the mind to stay alert. Contemplation gives the mind an opportunity to understand that its job is simply to facilitate the exchange between the internal and external world. Through the practice of contemplation we come to know that the role of the mind is simply to watch and register whatever passes between these two realms—nothing more.
The goal of yoga is not to control, restrain, or confine the mind but to calm the vṛttis—the mind's roving, revolving tendency. Gaining mastery over the mind entails overcoming the mind's tendency to roam aimlessly from one object to another, for as the yogis tell us, a disturbed, distracted, mind is not fit to practice yoga.
As a practical matter, however, body, mind, and consciousness are intermingled. We never experience one in isolation from the other two. We are mainly occupied by the concerns of the body because we are more sensitive to it than to the mind. Therefore practicing the core of yoga—attaining mastery over the modifications of the mind—becomes secondary to dealing with the needs and demands of the body. That is why the practices that help us become healthy and strong at the physical level have come to be called "yoga"; they help us minimize the obstacles to attaining mastery over the mind's modifications. Thus asana, breathing exercises, relaxation, concentration techniques, and the principles of good nutrition are all a part of yoga. However, a sincere student must remember that ultimately yoga means "union." The ultimate union is between the individual and the supreme, and the mind is the essential tool for bringing this union about.