Bhagavad Gita Chapter 2 Verse 66
भगवद् गीता अध्याय 2 श्लोक 66

नास्ति बुद्धिरयुक्तस्य न चायुक्तस्य भावना।
न चाभावयतः शान्तिरशान्तस्य कुतः सुखम्।।2.66।।



हिंदी अनुवाद - स्वामी रामसुख दास जी ( भगवद् गीता 2.66)
।।2.66।।जिसके मनइन्द्रियाँ संयमित नहीं हैं ऐसे मनुष्यकी व्यवसायात्मिका बुद्धि नहीं होती। व्यवसायात्मिका बुद्धि न होनेसे उसमें कर्तव्यपरायणताकी भावना नहीं होती। ऐसी भावना न होनेसे उसको शान्ति नहीं मिलती। फिर शान्तिरहित मनुष्यको सुख कैसे मिल सकता है


English Translation of Sanskrit Commentary By Sri Shankaracharya's
2.66 Ayuktasya, for the unsteady, for one who does not have a concentrated mind; na asti, there is no, i.e. there does not arise; buddhih, wisdom, with regard to the nature of the Self; ca, and; there is no bhavana, meditation, earnest longing [Longing to have a continuous remembrance of the knowledge of Brahman which arises in the mind from hearing the great Upanisadic sayings (maha-vakyas).] for the knowledge of the Self; ayuktasya, for an unsteady man. And similarly, abhavayatah, for an unmeditative man, who does not ardently desire the knowledge of the Self; there is no santih, peace, restraint of the senses. Kutah, how can there be; sukham, happiness; asantasya, for one without peace? That indeed is happiness which consists in the freedom of the senses from the thirst for enjoyment of objects; not the thirst for objects  that is misery to be sure.
The implication is that, so long as thirst persists, there is no possibility of even an iota of happiness!
It is being stated why a man without concentration does not possess wisdom:


English Translation of Commentary  - Dr. S. Sankaranarayan
2.66 See Comment under 2.68


English Translation of Ramanuja's Sanskrit Commentary
2.66 In him who does not focus his mind on Me but is engaged only in the control of senses by his own exertion, the Buddhi or the right disposition that is concerned with the pure self never arises. Therefore he fails in the practice of meditation on the self. In one who cannot think of the pure self, there arises the desire for sense objects; in him serenity does not arise. How can eternal and unsurpassed bliss be generated in him who is not serene but is attached to sense-objects?  [The idea is that without the aid of devotion to God, the effort to control the senses by ones will power alone will end in failure.]

 Sri Krsna speaks again of the calamity that befalls one who does not practise the control of the senses in the way prescribed above:


Transliteration Bhagavad Gita 2.66Naasti buddhir ayuktasya na chaayuktasya bhaavanaa;
Na chaabhaavayatah shaantir ashaantasya kutah sukham.


Word Meanings Bhagavad Gita 2.66na—not; asti—is; buddhiḥ—intellect; ayuktasya—not united; na—not; cha—and; ayuktasya—not united; bhāvanā—contemplation; na—nor; cha—and; abhāvayataḥ—for those not united; śhāntiḥ—peace; aśhāntasya—of the unpeaceful; kutaḥ—where; sukham—happiness