In plain words
In just the same way, five thousand years ago, a satellite called Naraka came near the earth and caused the people great fear and alarm. To end the people's distress and give them courage and zeal, Kṛṣṇa came to their aid and cared for them. That holy, auspicious day is what we celebrate as the slaying of Narakāsura, Dīpāvali.
That is to say, tamaso mā jyotir gamaya: the divinity that removes the Ajñāna and the darkness that have covered the Manas and gives brightness and radiance is what is called jyoti. The hand that lights one lamp is far nobler than the hand that puts out a thousand lamps. On Dīpāvali day we enjoy each light as a gift. These things go on in keeping with various local loyalties.
But looking at it as history, people think that Narakāsura was a demon. Where does this demon live? Prāgjyotiṣapura was his chief city. What is the meaning of Prāgjyotiṣa? Prā, before. Jyoti, light. Ṣā, those who have forgotten. Forgetting the light that is before you: that is Prāgjyotiṣapura. What is the light before us? The primal light. The primal light itself is the light of the Ātma. Forgetting the light of the Ātma is itself the mark of the demonic. Through forgetting the Ātma, many demonic traits grow in us. The root cause of the unrest of today's world, its misconduct and its Asatya, is this alone: forgetting the Ātma. We build up the body-self, neglect the jīvātma, and leave the Paramātma aside altogether. Every man: ahaṃ jīvātma, Ahaṃ dehātma: he travels only as far as these two. He does not reach the place that says ahaṃ Paramātma.
The reason is that in man there are five sheaths. Annamaya, prāṇamaya, manomaya, vijñānamaya, ānandamaya. The annamaya is this body. Of all the nourishment the body needs, whatever else may slip, this one never does. We keep it well fed. Then the prāṇamaya. Without it there is no body. We set about guarding prāṇa too, as far as we can.