The mind, Arjuna says in 6.34, is 'restless, turbulent, powerful, and obstinate — as hard to master as the wind.' Krishna does not disagree. He grants that the mind is difficult to hold, but insists it can be trained through 'practice and dispassion' (abhyasa and vairagya). The Gita's teaching on mind control is realistic, patient, and grounded in daily discipline.
Why does the Gita treat mind control as central? Because every path — action, knowledge, devotion, meditation — rises or falls with the stability of the mind. A wandering mind cannot offer action selflessly; it drifts into calculation. A wandering mind cannot dwell in the Self; it fragments. A wandering mind cannot love God; it loves a hundred lesser things instead. Krishna's diagnosis in Chapter 2 is that the senses drag the mind, and the mind drags the intellect — so the discipline must begin with the senses.
But Krishna is not a rigorist. He does not ask for the extinction of the mind, only its friendship. 'The self is the friend of the self — and also its enemy' (6.6). The training is a matter of turning the mind gently and repeatedly toward the Self, until the habit of scattering is replaced by the habit of centring. Read these verses as a graduated program — from the diagnosis, through the practice, to the fruit.