In plain words
All the norms of society have gone down into the Gaṅgā; contentment itself has vanished from the human race; character and moral values lie shattered; humanness has withered away among men.
Students!
Every human being in the world needs food. Of all the needs that belong to life, the one most needed is food. Man is not one to be content merely because he has eaten. Merely because his stomach is full, he is not happy at all. The stomach is filled, true, but the mind is not filled, and the heart has not ripened. To eat and then sit is not human nature. We must eat and move about. Having eaten and moved about, we must work. While doing this work: What am I doing? Why do I do it? How do I do it? These are the three questions we must put to ourselves. When he enquires well into the questions what am I doing, why do I do it, how do I do it, he can win success and Ānanda in this work. In work of this kind he goes about the world and tries to recognise the good that is in it. The good he has recognised, he tries to make his own experience. He enjoys the Ānanda that has come through the karmas he has done. The Ānanda he has enjoyed, he shares with many others. This itself is the chief teaching the Taittirīya Upaniṣad gave. To begin in food and end in Ānanda: this alone is the supreme goal of life.
This Taittirīya Upaniṣad arose in the Taittirīya branch of the Kṛṣṇa Yajurveda. This Upaniṣad is very ancient. That is why every single thing in this Upaniṣad is the very form of a mantra. A mantra is not merely the eight syllables Om Namo Nārāyaṇāya or the five syllables Om Namaśśivāya; these alone are not mantras. ‘Manana trāṇa sammiḷitaṃ iti mantraḥ’: what has been dwelt on and made firm in the mind is itself the mantra. So every word spoken in this Upaniṣad is the very form of a mantra.