Sri Aurobindo translates Katha Upanishad, First Cycle, Second Chapter, Verses 1-4: “Yama speaks: ‘One thing is the good and quite another thing is the pleasant, and both seize upon a man with different meanings. Of these whoso takes the good, it is well with him; he falls from the aim of life who chooses the pleasant. The good and the pleasant come to a man and the thoughtful mind turns all around them and distinguishes. The wise chooses out the good from the pleasant, but the dull soul chooses the pleasant rather than the getting of his good and its having. And thou, O Nachiketas, hast looked close at the objects of desire, at pleasant things and beautiful, and thou hast cast them from thee: thou hast not entered into the net of riches in which many men sink to perdition. For far apart are these, opposite, divergent, the one that is known as the Ignorance and the other the Knowledge. But Nachiketas I deem truly desirous of the knowledge whom so many desirable things could not make to lust after them.’ ”
There is a proverb especially circulated among spiritual seekers, that the “good” tastes bitter, but has a sweet effect; while the “pleasant” tastes sweet, but has a bitter effect. The Vedic Rishis and the seers of the Upanishads spent considerable time resolving the issues of what is the “good” and how to achieve it in one’s life versus those things that act as distractions. Eventually this led to the conclusion that following the desires of the physical and vital being, or the ambitions presented by the mind, may yield short-term enjoyment, but they simply do not last, and act as a serious detriment to inner peace and spiritual growth. Transitory enjoyment was thereby treated as the “pleasant” while the hard path of tapasya, concentration of conscious force, was treated as the “good”. To carry out this tapasya, the seeker would need to focus his energies and not simply work to satisfy the promptings of desire. In its more extreme forms, this led to the idea of sannyasa, or renunciation of the life of the world to pursue the spiritual seeking exclusively. This extreme version implies that there is a distinct duality whereby the Spirit is one side of the duality and the “life of the world” is the other. And for the seeker who is entering the path, an exclusive concentration on things spiritual may be both beneficial and necessary.
Eventually, however, the unity of the Spirit, “all this is the Brahman” combined with “One without a second” needs to be reintegrated, and the life of the world then can be taken up once more, but not from the standpoint of the satisfaction of the individual desires of the ego-personality, but from the standpoint of the unity of all in the manifestation of the Divine. This involves a much more subtle understanding of “good” and “pleasant” than the traditional “duality” approach needs to apply.
Sri Aurobindo, The Upanishads, Katha Upanishad, pp. 213-241, and Kapali Sastry, Lights on the Upanishads, pp. 104-129