In plain words
When we set our intellect right, understand the principle of the body, and try to look into the divine principle of God as well, there is a chance of gaining some attainment or some fruit from it; but if we keep increasing our delusions about the body day by day, pay no heed at all to the purity of the intellect, smear it with the needless dirt of sense-desires, and then grope about in our life crying, ‘God! God!’, mercy will not flow.
So first of all, before we live in this world, we must understand at the very outset the principle of the body, the mind, the intellect and the citta.
‘The one who lives in the world must first be a man; the one who keeps praising all the evil deeds of demons, he is the fool; to know oneself: that itself is a path to Mukti.’
One of those who were Śaṅkara's disciples, resolving that within such a principle the inquiry into our body is most necessary, gave the world a way that stirs revulsion: he gave childhood, youth, manhood and old age strange and extreme meanings, and so offered an opening for giving up the body. However long we live, the delusion that there is still more, that there is something left for us to achieve, may be called the very depths of infatuation. But while the body lasts, it is most necessary for us to know God, to understand something of the principle of the body too, and to regard this body as an instrument on the path that takes us to God.
This frail body made of the five elements: no one knows when it will be cast off. They set its limit at a hundred years, but do not trust that word in your heart. In childhood, in youth, in age, or in decrepitude, in a town, in a forest, or in the midst of the waters: no one knows when it will be cast off. For man death alone is certain; one who is wise must know himself while the body lasts….