Bhagavad Gita 6.34
चञ्चलं हि मनः कृष्ण प्रमाथि बलवद्दृढम्। तस्याहं निग्रहं मन्ये वायोरिव सुदुष्करम्।।6.34।।
cañcalaṃ hi manaḥ kṛṣṇa pramāthi balavaddṛḍham| tasyāhaṃ nigrahaṃ manye vāyoriva suduṣkaram||6.34||
cancalam hi manah krishna pramathi balavaddridham tasyaham nigraham manye vayoriva sudushkaram6.34
Meaning
Arjuna describes the mind as restless, turbulent, powerful, and obstinate. He considers controlling it to be as difficult as controlling the wind.
क्योंकि हे कृष्ण! यह मन चंचल और प्रमथन स्वभाव का तथा बलवान् और दृढ़ है; उसका निग्रह करना मैं वायु के समान अति दुष्कर मानता हूँ।
This is verse 34 of 47 in Chapter 6 (Dhyana Yoga) of the Bhagavad Gita.