All the power of knowledge and wealth once made has passed away — all the sciences of the ancients, lost, lost forever. Nobody knows how. That teaches us a grand lesson. Vanity of vanities; all is vanity and vexation of the spirit. If we have seen all this, then we become disgusted with this world and all it offers us. This is called Vairâgya, non-attachment, and is the first step towards knowledge.
The natural desire of man is to go towards the senses. Turning away from the senses takes him back to God. So the first lesson we have to learn is to turn away from the vanities of the world. (IX, 219)
The Four Disciplines
When have you reached knowledge? When you are equipped with those four disciplines [i.e. the four qualifications for attainment discussed in Vedantic literature: discrimination between the real and the unreal, renunciation, the six treasures of virtue beginning with tranquility, and longing for liberation]. You must give up all desire of enjoyment, either in this life or the next. All enjoyments of this life are vain. Let them come and go as they will.
What you have earned by your past actions none can take away from you. If you have deserved wealth, you can bury yourself in the forest and it will come to you. If you have deserved good food and clothing, you may go to the north pole and they will be brought to you. The polar bear will bring them. If you have not deserved them, you may conquer the world and will die of starvation. So, why do you bother about these things? And, after all, what is the use of them? (IX, 218)