Having told Arjuna that a Sthita Prajna is one with an unruffled mind, one who has completely overcome all desires and passions, Sri Bhagavan says to Arjuna that such a person withdraws his mind from external thoughts in order to contemplate the Atman within, which is Full and All-pervasive, in the same manner as a tortoise withdraws its limbs within its shell at the slightest sign of danger.
We desire a thing because of a feeling of incompleteness without it. But when we realise that what we ordinarily understand as "We" is nothing but the Absolute Bliss, the illusive pleasures after which the senses go lose their charm. Fire can never be quenched by giving it more fuel; the more we feed it, the more it burns. Similarly, our desires only increase by enjoyment.
At the same time, Bhagavan points out to Arjuna, and through Arjuna to all of us, that the path of self control is not strewn with roses. It comes only out of constant practice. Failure should not deter us; we should try, try and try and again till we succeed.
While desire fulfilled leads to further desire, desire frustrated turns into anger, like the rebound of a ball thrown at a wall. A person in the grip of desire or anger loses his reasoning power and consequently all his actions will be in the wrong direction. When desires become subordinate to the mind, the mind begins to dwell upon the Atman undisturbed and a person steeped in the contemplation of the Atman realizes the Supreme.
– Sri Chandrasekharendra Saraswati Mahaswamiji (20 May 1894 – 8 January 1994), or the Sage of Kanchi, was the 68th Jagadguru of the Kanchi Kamakoti Peetham.