Chapter 6 · The Yoga of Meditation · Arjuna said
Bhagavad Gita 6.34 — Mind like the wind
चञ्चलं हि मनः कृष्ण प्रमाथि बलवद् दृढम्। तस्याहं निग्रहं मन्ये वायोरिव सुदुष्करम् ॥
cañcalaṃ hi manaḥ kṛṣṇa pramāthi balavad dṛḍham | tasyāhaṃ nigrahaṃ manye vāyoriva suduṣkaram ||
Meaning
The mind is restless, Krishna — turbulent, strong and stubborn. Controlling it seems to me as hard as controlling the wind.