In plain words
That is why the Buddha too
All is sorrow, sorrow; all is momentary, momentary; all is impermanent, impermanent:
went on proclaiming this.
In man two kinds of principle are held together. One is permanent, the other impermanent. One is the Ātma, the other the non-Ātma. One is the body, the other the one who dwells in the body. One is the deha, the other the dehī. One is the field, the second the knower of the field. So it is man's chief duty, made of this duality as he is, to enquire which is true, which is untrue, which is permanent and which is impermanent, and having enquired, to accept the truth and give up the untruth. This very thing the Bhagavad Gītā has taught in the words Kṣetra-kṣetrajña-vibhāga-yoga, Guṇatraya-vibhāga-yoga and the power of discerning the permanent from the impermanent. So the aim of education is to recognise the true nature of man. This itself is right education. In the world, many paths have come into being for giving up one's strength, one's intellect, one's all, experiencing yoga and merging in divinity. Not by action, not by offspring or wealth: by sacrifice alone have some attained immortality. Thus sacrifice is the chief path for us.
We must keep going on, without a break, in the enquiry into what we must give up and what we must accept. We must try to recognise all the objects seen in this world of visible forms that appears to us, the experiences we go through and the joy we taste. Today we feel that the world is wasting away in endless unrest and in hardships and sorrows of some kinds. We must enquire what the cause of this is.
What is man? Man is Manas itself. What is Manas? The gathering of resolves itself. What are resolves? This transformation itself is the conduct we practise in our daily life. The fruit of this conduct itself is the joys and sorrows we experience in our everyday life. What is the cause of these joys and sorrows? Our behaviour itself. What is the cause of behaviour? Our thoughts themselves. So when man's behaviour and thoughts are right, the world will be well and safe. When we look into a tree, a river or an animal with a long view, we understand what a life of sacrifice they lead.
For the good of others the trees bear fruit; for the good of others the rivers flow; for the good of others the cows give milk; for the good of others is this body.