Bhagavad Gita 18.37

यत्तदग्रे विधोमिव परिणामेऽमृतोपमम् |
तत्सुखं सात्विकं प्रोक्तमात्मबुद्धिप्रसादजम्

Translation

That which seems like poison at first, but tastes like nectar in the end, is said to be happiness in the mode of goodness. It is generated by the pure intellect that is situated in self-knowledge.