यत्तदग्रे विषमिव परिणामेऽमृतोपमम्।तत्सुखं सात्त्विकं प्रोक्तमात्मबुद्धिप्रसादजम्॥
yat tad agre viṣam iva pariṇāme 'mṛtopamam tat sukhaṃ sāttvikaṃ proktam ātma-buddhi-prasāda-jam
Word by word
The verse says
What tastes like poison at first and like nectar in the end: that happiness is called clear. It is born of the settled clarity of knowing yourself.
In plain words
The image is exact, and the order is everything.
Poison first. Nectar after. Not pleasant throughout, and not a reward for suffering either. The same thing changes taste.
And its source is named: it comes from a mind that has settled and from knowing what you are. Not from circumstances improving.
Where you've felt this · in health
The first four times you sit down to do a difficult thing you have been avoiding, it is genuinely unpleasant and you get very little done. Somewhere around the second week the sitting down stops costing anything. The work has not changed. The approach to the desk has.
Going deeper
The same activity tasting of poison and then of nectar is the most practically useful image in this chapter.
It explains a failure that happens to almost everyone. You try the right thing, it feels bad, and you conclude it is not for you. The conclusion is drawn from accurate evidence at the wrong moment. The early taste is real; it is simply not the taste of the thing.
The second half locates the source. This happiness comes from clarity about yourself, which is why it cannot be bought and why it does not evaporate when conditions change. Chapter 2 made the same point about a steady mind: what does not depend on circumstances cannot be removed by them.
So the usable rule is about when to judge. An early verdict on a difficult practice is almost always a verdict on the difficulty rather than on the practice, and those are not the same thing.