Sanskrit
यदग्रे चानुबन्धे च सुखं मोहनमात्मनः । निद्रालस्यप्रमादोत्थं तत्तामसमुदाहृतम् ॥ ३९ ॥
yad agre cānubandhe ca sukhaṃ mohanam ātmanaḥ nidrālasyapramādotthaṃ tat tāmasam udāhṛtam
Translation
That pleasure which both at first and afterwards is delusive of the self, arising from sleep, indolence and heedlessness, that is declared dark.
Annie Besant · The Bhagavad-Gita, translated by Annie Besant (4th ed., 1922) — Wikisource · Public Domain
Explanation
Tamasic happiness has no redeeming arc at all — delusive both at the start and throughout, arising from sleep, indolence, and heedlessness (pramada). With this the threefold happiness analysis closes exactly where chapter 14 left the sattva-rajas-tamas destinies: what a person finds pleasurable, examined honestly, turns out to be one of the most reliable diagnostics of which guna currently governs them — a thread this final chapter has now pulled taut across knowledge, action, the actor, intellect, resolve, and, finally, joy itself.