In plain words
The weapon called the mind was given of old to man alone; this mind: only the man who keeps it in discipline is the victor on earth; that any mere man who is a slave to the mind sought Śānti and happiness and found them is not to be heard of, even in a dream.
This body of the five elements, with its senses, is not separate from the mind. This very body is the mansion the mind has built for its own play. This body is like an armour for the mind. For every body, this mind alone is the support. This mind alone is the cause. Just as a crop without water has an existence of unreal form, so humanness without the mind, the human state, has an existence of this kind. The mind alone is the root and support of the world's dealings, its activities and its laments. Just as a school with no teacher, a temple with no God, a wire with no current and a crop with no water are useless, so a man with no mind is a life that has died. So man's effort to turn the humanness bound up with such a mind into divinity is essential too.
But commonly man feels himself to be something bound in the body. That is why he spends his time, and his karma too, on the welfare of this body of the five elements. Believing the body alone to be true and lasting, he makes efforts of every kind for its sake. Such a one relies only on the life-breath of the body made of food and makes his life futile. One who relies on the vijñānamaya, which is Buddhi, and through that vijñānamaya conquers the manomaya: he alone can become wise. He is the man of wisdom. This principle of Prajñāna comes about only through good thoughts. Good thoughts are man's chief wealth. These good thoughts are not ordinary. They are very strong. Very pure. Very divine. Splendid. Ever new. However we use them, it gives a result of that kind. Such good thoughts grow through good company as time goes on.