In plain words
So if the person who has resolved to push the boulder he stands on steps down to one side and brings his strength to bear on the boulder, then pushing that boulder becomes something possible in this world. Seat the horse that pulls the cart inside the cart, and can it pull it? So, just as a horse that pulls a cart can pull it only when it is harnessed to the cart, and cannot pull it if you seat it in the cart and tell it to pull, so the divine principle of the jīva called humanness was placed here precisely to pull this cart called the body; how foolish it is for us to seat it inside this cart called the body and try to drive the cart: you can think it over for yourselves. Merely by sitting in a car, you do not become the car. You may be the one who drives the car, but you can never be the car. For a man standing on the boulder called the body to keep standing on the body itself, to lock up his whole life in the delusion of the body itself, and to push that boulder called the body, is a thing impossible. So when the person trying to push aside this boulder called body-delusion thinks of himself as a form apart from the body, and regards himself as one who has nothing whatever to do with the delusions of the body, then pushing the body aside has a meaning. So that we may know how to use this bodily principle on the right path and reach our own eternal abode, whose very form is Satya, the Bhagavad Gītā has given us many kinds of ideals. A student from Calcutta, putting forward his doubt: ‘In the Bhagavad Gītā, Kṛṣṇa Paramātma: just as He gives up the old body and takes on a new body, He gives up the old garment and puts on a new garment. So the body is like a garment. So you need not desire this worn-out garment in the least; in desiring it there is nothing proper for you at all’: that, he said, is how Kṛṣṇa had taught. Now, when this body is an old garment, it is indeed right for man either to cast it off or to give it up. When this body is new, that is, at a young age, a body of 20 years, or 15 years, or 9 years: is it old or new? That is the question.