“Yoga is restraining the mind-stuff (Chitta) from taking various forms (Vrttis)“
First, we need to understand what Chitta is, and what are these Vrttis. The waves of thought in the Chitta are called Vrtti (“the whirlpool” is the literal translation). What is thought? Thought is a force, as is gravitation or repulsion. It is absorbed from the infinite storehouse of force in nature; the instrument called Chitta takes hold of that force, and, when it passes out at the other end it is called thought. This force is supplied to us through food, and out of that food the body obtains the power of motion, and Other, the finer forces, what we call thought.
As organ of perception, we have “Indriya”, the sense organs, like eye, ear tongue etc. These instruments of perception give a sensation of objectivity around us that gives a blow to the mind, and the mind gives out “the reaction”. If a stone is thrown into the water the water is thrown against it in the form of waves. The real Universe (or can be said micro universe around us) is the occasion of the reaction of the mind. . Matter is the “permanent possibility of sensation,” said John Stuart Mill. Take an oyster for example. You know how pearls are made. A grain of sand or something gets inside and begins to irritate it, and the oyster throws a sort of enameling around the sand, and this makes the pearl. This whole universe is our own enamel, so to say, and the real universe is the grain of sand. We will never understand it, because, when we try to, we throw out an enamel, and see only our own enamel.
So, we all got the real self, or our spiritual self, or a soul, behind the mind. This spiritual self needs to interact with the infinity, via the instrument called Chitta or mind. We can’t see the bottom of the lake, because its surface is covered with ripples. It is only possible when the rippled have subsided, and the water is calm, for us to catch a glimpse of the bottom. If the water is muddy, the bottom will not be seen; if the water is agitated all the time, the bottom will not be seen. If the water is clear, and there are no waves, we shall see the bottom. That bottom of the lake is our own true Self; the lake is the Chitta, and the waves are the Vrttis.
Chitta or mind has three states-
Tamas- the darkness.
Rajas- gives as power and enjoyment.
Sattva- serenity and calmness
Though we feel the least prominence of sattva, it is the strongest form of Chitta and surprising, it’s the most active one. It is the greatest manifestation of power to be calm. It is easy to be active. Let the reins go, and the horses to take their move. Anyone can do that, but he who can stop the plunging horses is the strong man. Which requires the greater strength, letting go, or restraining? The calm man is not the man who is dull. You must not mistake Sattva for dullness, or laziness. The calm man is the one who has restraint of these waves. Activity is the manifestation of the lower strength, calmness of the superior strength.
This Chitta is always trying to get back to its natural pure state, but the organs draw it out. To restrain it, and to check this outward tendency, and to start it on the return journey to that essence of sattva is the first step in Yoga, because only in this way can the Chitta get into its proper course.