That which is like poison at first but in the end like nectar that happiness is declared to be Sattvic, born of the purity of one's own mind due to Self-realisation.
In simple words
Krishna describes pure happiness: "The happiness that feels like poison at the beginning — because it requires effort and discipline — but becomes like nectar in the end. That happiness comes from the clarity of a mind that knows itself. That is pure happiness."
Word-by-word meanings
यत्whichतत्thatअग्रेat firstविषम्poisonइवlikeपरिणामेin the endअमृतोपमम्like nectarतत्thatसुखम्pleasureसात्त्विकम्Sattvicप्रोक्तम्is declared (to be)आत्मबुद्धिप्रसादजम्born of the purity of ones own mind due to Selfrealisation
18.37 यत् which? तत् that? अग्रे at first? विषम् poison? इव like? परिणामे in the end? अमृतोपमम् like nectar? तत् that? सुखम् pleasure? सात्त्विकम् Sattvic? प्रोक्तम् is declared (to be)? आत्मबुद्धिप्रसादजम् born of the purity of ones own mind due to Selfrealisation.Commentary Agree vishma iva In the beginning it is attended with much pain as one has to abandon the sensual objects and comforts and practise severe austerities and rigorous Sadhana. He has to undergo a severe ordeal when he practises Yama? Niyama? Tapas and various other vows. He has to cultivate dispassion or indifference to sensual pleasures. This gives him much pain at first. The practice of concentration and meditation also gives pain the beginning. Subjugation of the senses is also very troublesome. Nux vomica is very bitter. One feels much discomfort when he takes a mixture that contains nux vomica. But he derives much pleasure in the end when he gets vigour and good appetite and when his dyspepsia is cured. Even so the aspirant drinks the nectar of immortality in the end? attains the highest knowledge? rejoices in the,Self to his hearts content and enjoys supreme peace and eternal bliss.Proktam It is declared by the wise.Atmabuddhiprasadajam Born as purity of ones own intellect or born of the direct? perfect and clear knowledge of Brahman or the immortal? selfluminous? eternal and supreme Self or the Absolute. The individual self experiences Sattvic happiness when it realises union with the highest Self.The pleasure so born is Sattvic. (Cf.VI.1?2)
Contemporary scholarly and practical interpretations for modern seekers.
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
Modern
That happiness which appears like poison in the beginning but becomes nectar in the end—this is declared to be sattvic happiness, born from the clarity of the intellect united with the Self.
Here it is worthy of note that sattvic happiness is never truly like poison. However, because the natural tendency of human beings is outward-turned, they find difficulty in practicing the means of sattvic happiness such as knowledge, dispassion, and meditation. Therefore, to such a weak person, this sattvic happiness appears painful like poison at first, but this is not the reality. For example, children find the study of lessons painful because they are attached to play.
In the end, it becomes like nectar. That is, when maturity comes through the practice of knowledge, dispassion, and other disciplines, and one experiences true peace of mind, then it becomes joyful like nectar. This happiness is called sattvic.
Born from the grace of the intellect united with the Self: Most people understand grace (prasad) merely as the food distributed after the completion of ritual worship. But here the meaning of grace is broad and profound.
The intellect that becomes absorbed in the nature of the Self through self-inquiry is called the intellect united with the Self. The grace of that intellect means serenity and purity. When the intellect becomes calm, pure, and steady, the happiness that is experienced is sattvic happiness born from the grace of the intellect united with the Self. Such supreme happiness is attained only by the well-educated, the well-cultured, and the sattvic person.