Bhagavad Gita 2.60
यततो ह्यपि कौन्तेय पुरुषस्य विपश्चितः। इन्द्रियाणि प्रमाथीनि हरन्ति प्रसभं मनः।।2.60।।
yatato hyapi kaunteya puruṣasya vipaścitaḥ| indriyāṇi pramāthīni haranti prasabhaṃ manaḥ||2.60||
yatato hyapi kaunteya purushasya vipashcitah indriyani pramathini haranti prasabham manah2.60
Meaning
The turbulent senses can forcibly carry away the mind of even a discerning person who is striving for self-control. Vigilance is always necessary.
हे कौन्तेय! प्रयत्न करने वाले विवेकी पुरुष के मन को भी ये प्रमाथी (उद्वेलित करने वाली) इन्द्रियाँ बलपूर्वक हर लेती हैं।
This is verse 60 of 72 in Chapter 2 (Sankhya Yoga) of the Bhagavad Gita.