2.48. Perform action O Dhananjaya, abandoning attachment, being steadfast in YOGA, and balanced in success and failure. Evenness of mind is called YOGA.
2.49. Far lower than the YOGA-of-wisdom is action, O Dhananjaya. Seek thou refuge in wisdom; wretched are they whose motive is the ‘fruit’.
Work done with a mind undisturbed by anxieties for the results is indeed superior to the work done by a dissipated mind, ever worrying over the results. Here the term, ‘Buddhi Yoga’ has tickled some commentators to discover in it a special Yoga as advised by the Geeta. I personally think that it is too much of a laboured theory. Buddhi – as defined in the Upanishads – is the determining factor in the ‘innerequipment ’; Nishchyatmika is ‘intellect’; Samshayatmika is ‘mind’. Thus when the thought flow is in a state of flux and agitated, it is called the ‘mind’. When it is single-pointed, calm, and serene in its own determination, it is called the ‘intellect’. Thus Buddhi Yoga means ’to be established in devotion to the intellect’. Being steady in your conviction, with your mind perfectly under the control of your discriminative intellect, to live thus as a master of your inner and outer world is called Buddhi Yoga. In Buddhi Yoga we pursue our duties without ever losing sight of our ultimate Goal in Life.
Bhagavad Gita (Holy Geeta) translation and commentary by Chinmayananda