Verse
चंचलं हि मनः कृष्ण प्रमाथि बलवद् दृढम् ।तस्याहं निग्रहं मन्ये वायोरिव सुदुष्करम् ॥
caṃcalaṃ hi manaḥ kṛṣṇa pramāthi balavad dṛḍhamtasyāhaṃ nigrahaṃ manye vāyoriva suduṣkaram
Restless indeed is the mind, O Krishna; it is vehement, strong and unconquerable; I deem it as hard to control as the wind.
Gītā 6·34