37. This verse describes three types of desire – sattvika, rajasika and tamasika. Krsna gives three similes for each of them.
Sattvika desire is like smoke around fire. Fire can be seen even while the smoke covers it. A passing breeze can remove the smoke. Similarly even though sattvika desire shrouds Atman, the brilliance of Divinity can be seen through it. This desire – to realize Atman, serve the guru, emancipate society etc – goes away effortlessly.
Rajasika desire is like dust on a mirror. Dust obscures the reflection and you need to wipe it off. Rajasika desire blurs the vision of Atman and you need to put in effort to refine and eliminate it. Desire for wealth, power and position are examples of rajasika desire.
Tamasika desire is likened to a foetus in a womb. It takes a great deal of effort as well as time and you cannot see the embryo at all. Tamasika desire totally shrouds Atman and needs a great deal of time and effort to eradicate it. Sloth, indifference, inertia and the like are tamasika desires.
This is covered by that. ‘This’ refers to Atman while ‘that’ means desire to indicate that Atman is nearer to us than desire.
39. Desire is unquenchable. The more you have the more you want. It agitates the mind and disables the intellect. It is like a virus that corrupts your database. Knowledge that you have so painstakingly acquired then becomes inaccessible leading to costly errors. A brilliant surgeon is unable to operate on his own family members. A bereaved person is unable to function normally. To the extent you are agitated your thinking ability is compromised and you commit mistakes. All humans have disturbed minds and thus the world over there is paucity of clear thinking.
When rajas and tamas predominate you make disastrous decisions leading to failure and sorrow. Just one desire can destroy you. Hence it is referred to as nityavairin, constant enemy, of the wise. Only in sattva where you have risen above desire and the mind is calm are you able to think clearly and act decisively.
The first step is to have the intellect check, control and regulate desire. Then desire takes the benign form of a goal, ideal or ambition. The next stage is reduction of desire through Karma Yoga, upgrading desire by Bhakti Yoga and redirecting desire to the higher by Jnana Yoga. The last remnants of desire go through meditation. Then you become Atman.