Arjuna asks Krishna to describe the characteristics of the perfect yogi, Sthitaprajna. Krishna points out that a stable human behaviour implies separation of “I” from the mind. When the mind engages in selfish desires it evaluates success and failures and never gets the freedom. The mind needs diversion from selfish to unselfish desires to get the freedom.
“Manojaya eva mahajayah—Conquest of mind is the greatest victory. Mind is one of the ashta-prakritis earth, water, fire, air, ether, mind, reason and egoism these constitute the eight-fold division of My Eternal Energy” says Sri Krishna (Bhagavad Gita, Chapter 7 verse 4).
The mind, manas, is controlled by intelligence, buddhi, and has control over our sense organs, indriyas. If our sense organs are horses of a chariot, the mind is the leash that is held by intelligence, the charioteer. The chariot will move in the right direction only if the charioteer has control over the horses through the leash. The mind is like the supervisor in the factory of life, and directs the indriyas. The mind does a wonderful job of carrying out directions, but it is not supposed to be the key decision-maker in the factory. That is the job of intelligence. If intelligence is clouded, then the mind has a habit of listening to whoever is speaking the loudest in the factory.
There is conflict between intelligence and mind that is judged by our consciousness. This is never seen in animals. Let us suppose a landlord who happens to leave his house for a few days orders both his housekeeper and the dog not to go out of the house in his absence. Even though both have violated the order, the dog has no inner conflict and sleeps happily, but the housekeeper is sleepless. He feels guilty and is also ticked off for not following orders. The mind should always listen to intelligence and order the indriyas, and then there would be no conflict of mind and intelligence. When we say we have a disturbed mind then we have done something that our intelligence does not want us to do.
In the Yaksha Prashna episode in the Aranya Parva of the Mahabharata, Yama asks Yudhisthira what is the swiftest of all in the universe? Yudhisthira answers that the mind is the swiftest of all, manovega. The mind can travel at unimaginable speed; this has made the mind inconstant. Restless and unpredictable, the mind is an obstruction to peace. Mantra Japa is one way of controlling the restless mind.
A story in the Skanda Purana illustrates this: After the battle of Kurukshetra, Yudhisthira contemplates on performing the Ashwameda Yagya. Krishna who wanted Bheema to know the importance of Mantra Japa asks him to bring Purusha Mruga who lives in Himalayas for the Yagya. Krishna warns Bheema that Purusha Mruga travels at the speed of mind and to bring him he has to travel at that speed failing which the Purusha Mruga would kill and devour him. Bheema who could travel at the speed of wind (vayuvega) thinks he could bring him. Bheema goes in search of Purusha Mruga and happens to meet his brother Hanuman and tells him about his mission. Hanuman tells Bheema that the only way to keep pace with Purusha Mruga is to place thousand Lingas through the route.
Being a devotee of Shiva, Purusha Mruga would halt at each Linga to chant the thousand names of Shiva thus allowing Bheema to keep pace with him. Bheema succeeded in the mission, his vayuvega could match Purusha Mruga's manovega since it was slowed down with Mantra Japa.