6.5, Sloka 5 & 6: Chapter 6:
In this sloka, Lord Krishna gives out who is the friend and foe of a person. He says “the mind” is the friend and enemy of a person. If a person can keep the mind’s desires under control, the mind becomes his friend. If the person cannot keep the mind’s desires under check the mind, in fact, acts like an enemy to the person. It basically destroys a person slowly and slowly. The person will not even know he is being destroyed but the desires of the person will destroy him slowly and slowly. One desire at the subtle level will lead to another desire at a higher level. The desires are indeed in the form of a chain, one higher form of desire feeding and building on a lower form of desire.
The desires of mind form the crucial link for a mind to be a friend of a person or enemy. A proper disciplined, cultivated mind is like a friend of a person. It elevates him from his desires and also keeps a check on desires. the cultivated mind keeps the basic, elemental desires at check so that they do not become big and engulf the person.
Lord Krishna asks people to elevate themselves their mind and does not degrade it. How does a person elevate the mind? elevating the mind is by making it “fast” from what it needs. Basically, a mind needs comforts and it makes a human being so many things to be in the comfort zone. Feed the mind virtues of life and values which make a great life. Feed the mind with a constant inquiry of what’s truth and what’s untruth. Using reason as a tool of the intellect, feed the mind constantly with what’s the truth. It makes progress gradually from what it is, a comfort-seeking brain to higher levels of truth-seeking.