Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 2

Sanskrit:

प्रायश: पुण्डरीकाक्ष युञ्जन्ते योगिनो मन: ।विषीदन्त्यसमाधानान्मनोनिग्रहकर्शिता: ॥ २ ॥

ITRANS:

prāyaśaḥ puṇḍarīkākṣayuñjanto yogino manaḥviṣīdanty asamādhānānmano-nigraha-karśitāḥ

Translation:

O lotus-eyed Lord, generally those yogīs who try to steady the mind experience frustration because of their inability to perfect the state of trance. Thus they weary in their attempt to bring the mind under control.

Purport:

Without the shelter of the Supreme Lord, a yogī easily becomes discouraged in the difficult task of fixing his mind on the Supreme.