Bhagavad Gita 3.39 · Krishna
A fire that is never full
आवृतं ज्ञानमेतेन ज्ञानिनो नित्यवैरिणा।
कामरूपेण कौन्तेय दुष्पूरेणानलेन च॥
āvṛtaṃ jñānametena jñānino nityavairiṇākāmarūpeṇa kaunteya duṣpūreṇānalena ca
Knowledge is covered by this constant enemy of the wise, son of Kunti, desire, a fire that is never satisfied.
What it means
Krishna adds a striking image. Desire is like fire. Feed it, and it doesn't calm down. It burns hotter. That's why even the wise must watch it. It wears the form of whatever we crave, and quietly covers our understanding, again and again.
The story
Krishna says even the wise face this enemy. It's a kind thing to tell Arjuna. Struggling with desire isn't a sign of failure. It's the shared work of every human being.
In your life
Imagine someone who gets the dream car and, within a month, starts browsing a better one. The fire wants more fuel. Next time you feel a craving, wait one day before you feed it. Watch what happens.
Feeding the fire only makes it hungrier.