In plain words
You say, “I alone am experiencing all these.” In the dream state you create yourself; without buying any bus ticket or plane ticket you go to Delhi, you wander all over America. But in deep sleep, without moving or stirring anywhere, you experience Ānanda. The one who experiences these three states is you alone. All that is experienced in the waking state is nothing but sensations of the senses. The mind is very fickle. To restrain such a mind, Ādi Śaṅkara made an arrangement in his āśrama. It was this: before the door, two disciples, one from either side, walking to and fro, “Take care! Take care!” they were to keep on saying. Once Śaṅkara, “I have so big an āśrama. I alone am the master of all this,” he thought. At that very moment, from outside, “Take care! Take care!” was heard. At once he recognised his mistake. Śaṅkara enquired well into human life, into birth and death, and into worldly bonds and kinship, and went on proclaiming the truth to the world.
Birth is sorrow, old age is sorrow, a wife is sorrow, again and again; at the last hour, great sorrow: therefore be watchful, be watchful! There is no mother, no father, no kinsman, no brother; no wealth, no house: therefore be watchful, be watchful!
This truth the ancient great sages taught to the students in the gurukula. That is why the educated of that day led sacred lives. The education of that day arose from “Ṛta”. That very thing we today call “Educare”. Edu'Care' means that we must always be careful. This very thing has been called the ABC of life. That is, it means Always Be Careful. Śaṅkara taught precisely this. Today we must teach the students this spiritual learning too, along with worldly education. Worldly education is negative, spiritual education positive. Worldly education is merely like a bulb.