Almost everyone has noticed that when they try to focus on an object or an idea in the present, their mind starts to wander. It's hard to keep the mind occupied with just one thought. Even the wise people of the past had problems. Arjuna said in the Gita that it is impossible to control the mind on earth. So, Krishna told him that even though it is hard to control the mind, it can be made quiet and steady by doing vairagya and abhyasa every day. He has, however, said that yoga is hard for people whose minds are not steady and under control. In the Yoga Sutra, Pantanjali says that you need these two things to control your mind. So, these are the very things that make up what yoga is all about.
Mind is like a dirty pond that has been stirred up. To clean the mind, you must first stop new impurities from coming in. Then, you must get rid of the impurities that are already there. Abhyasa is one of the things you can do to clean your mind. One of the smaller parts of abhyasa is dhyana. When a person has been practising concentration for a while, they reach this stage. At the beginning of dhyana, the mind is more stable and only has one thought about an object. We can now say for sure that dhyana has been reached. Here, the mind becomes very stable, like the flame of a lamp in a quiet room, and its contact with the object of experience becomes intense and complete.
There are two kinds of dhyana: sagunadhyana and nirgunadhyana. In the first dhyana, the mind's stillness is linked to an object of experience that can be felt with the senses. The second one makes no sense at all. It means that the mind is completely absorbed in itself. Here, the mind is not associated with any external object. In this state, it stops moving completely. This mind is supposed to stay still, quiet, and sensitive so that it can understand anything that has happened anywhere in the universe in the past, present, or future.