Almost everyone has experienced the fact that when one starts concentrating his mind on any immediate object or an idea, the mind starts wandering. It is very difficult to keep the mind busy with a single thought. The ancient sages too encountered the same problems. Arjuna, in Gita had mentioned that controlling the mind is an impossible thing on earth. Hence, he was advised by Krishna that though mind control is difficult, it can be made silent and steady by regular practice of vairagya and abhyasa. However, he has warned that yoga is very difficult for people whose minds are not steady and controlled. Pantanjali, in Yoga Sutra has emphasized these two qualities to achieve mind control. Hence ,these are the very qualities that make the essence of yoga.
Mind is like a disturbed pond with many impurities. First you need to stop the inflow of fresh impurities and then remove the existing impurities to clean the mind. Abhyasa is one of the practices for purifying the mind. Dhyana is one of the sub practices of abhyasa. This is a stage that a person reaches after practicing concentration for some time. At the start of dhyana, the mind is steadier and only a single thought...