Having restrained, having mastered, all of them, joined, his mind composed, let him sit intent on Me: I, Vāsudeva, the inmost Self of all, am the supreme for him, the one beyond whom he sees nothing, holding 'I am no other than that'. Let one so seated, the ascetic in whose control the senses come to be by the strength of practice, be one whose insight is settled. Now, of one about to be defeated, this is stated, the root of all ill.

Wishing to ward off every fault, having held in the senses, hard to conquer because they are joined with passion for objects, and having set the mind on Me, the auspicious resort of the mind, let him sit collected. When the mind is on Me as its object, being made pure by the burning away of all its taint and freed of passion for objects, it makes the senses obedient to itself. Then the mind, with the senses obedient, is able to behold the self. So it is said: 'as a kindled fire, helped by the wind, burns up the brushwood, so Vishnu, present in the mind, burns up all the taint of yogins'. The Lord therefore says, 'whose senses are under control, his wisdom is well established'. The Lord says that one who, without setting the mind on Me, sets out by his own effort, by main force, on the conquest of the senses, comes to ruin.

Then they are simply not to be mastered, one might think; so Krishna says, with 'those senses'. They can be mastered by much effort, and the implied sense is that one should make the effort. 'Joined' means joined by the application of the mind to Me. 'He whose supreme one, higher and more excellent than all, is Me' is the one who holds Me as supreme. Krishna states the fruit with 'for whose senses are under control'.