Here Lord Krishna is emphasising the importance of the mind regarding yoga or the science of the individual consciousness attaining communion with the ultimate consciousness. For one whose mind is uncontrolled it is not possible to practice yoga but that person who has controlled their mind by dispassion and regular practice and meditation can succeed in yoga by striving repeatedly.

It should not be thought that the mind of its own accord becomes controlled because that is not the case. For those who are unrighteous, who do not desire what is good for other created beings, who hate, who are debauchers, who are non-believers of the Vedic scriptures and other such persons, the opportunity for moksa or liberation from the endless cycle of birth and death in the material existence never manifests. This has been categorically confirmed in the Brahma Purana.

That the mind is difficult to control and direct due to its fickle and tempestuous nature is a fact unable to deny. But the possibility of taming it depends upon generating in the mind a feeling of affection and attachment by accustoming the mind to regularly reflect on the sublime, transcendental qualities of the atma or soul and then meditating upon the atma daily. In this way very soon an aversion will arise to focus on anything that does not facilitate atma tattva or realisation of the soul. This will happen naturally when the discerning mind perceives the imperfections inherent in all other topics and subjects. Lord Krishna is reiterating that for one who has not subjugated their mind this yoga or the science of the individual consciousness attaining communion with the ultimate consciousness by dhyana or meditation is extremely difficult to realise; but it is possible to achieve by one who has the vision of equanimity towards all beings and understands that the same fundamental spiritual basis is present everywhere as the atma existing in all living entities. Controlling the mind has already been elucidated by Lord Krishna in the process of selfless karma yoga as offerings of worship to the Supreme Lord. Lord Krishna has also instructed in chapter II.XXXX that there is no loss or diminution by the performance of this yoga; but the greatness of karma yoga there described is certainly that which embodies atma tattva and culminates in communion with paramatma the Supreme Soul by meditation.

Lord Krishna is confirming that it is not possible to become established in yoga or the science of the individual consciousness attaining communion with the ultimate consciousness by dhyana or meditation. To behold all with equanimity and dispassion is not possible for one whose mind is restless and uncontrolled. But through ceaseless striving and constantly practising of meditation it is possible to be successful in controlling it.