From Essence of Yoga, Swami Sivananda Saraswati

Yoga is the discipline of the mind, senses and physical body. Yoga helps in the coordination and control of the subtle forces within the body. Yoga brings in perfection, peace and everlasting happiness.

Yoga can help you in your business and in your daily life. You can have calmness of mind at all times by the practice of yoga. You can have restful sleep. You can have increased energy, vigour, vitality, longevity and a high standard of health. Yoga transmutes the animal nature into divine nature and raises you to the pinnacle of divine glory and splendour.

The practice of yoga will help you to control the emotions and passions and will give you the power to resist temptations and to remove the disturbing elements from the mind. It will enable you to keep a balanced mind always and remove fatigue. It will confer on you serenity, calmness and wonderful concentration. It will enable you to hold communion with the Lord and thus attain the summum bonum of existence.

If you want to attain success in yoga, you will have to abandon all worldly enjoyments and practise tapas and Brahmacharya. You will have to control the mind skilfully and tactfully. You will have to use judicious and intelligent methods to curb it. If you use force, it will become more turbulent and mischievous. It cannot be controlled by force. It will jump and drift away more and more. Those who attempt to control the mind by force are like those who endeavour to bind a furious elephant with a thin silken thread.

The aspirant on the path of yoga should be humble, simple, gentle, refined, tolerant, merciful and kind. If you have a curiosity to get psychic powers, you cannot have success in yoga. Yoga does not consist in sitting cross-legged for six hours or stopping the pulse or the beating of the heart or getting oneself buried underneath the ground for a week or a month. Yoga is a perfect practical system of self-culture. Yoga is an exact science. It aims at the harmonious development of the body, the mind and soul. Yoga is the turning away of the senses from the objective universe and the concentration of the mind within. Yoga is eternal life in the soul or spirit. Yoga aims at controlling the mind and its modifications. The path of yoga is an inner path whose gateway is your heart.