Bhagavad Gita Chapter 3, Verse 38

आवृतं ज्ञानमेतेन ज्ञानिनो नित्यवैरिणा | कामरूपेण कौन्तेय दुष्पूरेणानलेन च ||

āvṛtaṁ jñānam etena jñānino nitya-vairiṇā kāma-rūpeṇa kaunteya duṣpūreṇānalena ca

Knowledge is covered by this eternal enemy of the wise in the form of insatiable desire (kāma), which is like an insatiable fire, O son of Kunti.

Krishna reveals how desire operates: it covers wisdom like smoke covers fire. The wisdom is still there—you know what's right—but you can't access it. 'Āvṛtaṁ jñānam' means knowledge is covered, not destroyed. 'Nitya-vairiṇā'—the eternal enemy, because kāma is always trying to cloud your clarity. The verse uses a powerful image: 'duṣpūreṇānalena'—insatiable fire. Feed fire and it grows bigger, never satisfied. Same with desire. Get what you want, feel good briefly, then want more. That's why you do things you know are wrong—in that moment, wisdom is covered by desire's smoke.