Vivekachudamani 344

अहंबुद्ध्यैव मोहिन्या योजयित्वावृतेर्बलात् । 

विक्षेपशक्तिः पुरुषं विक्षेपयति तद्गुणैः ॥ ३४४ ॥ 

ahaṃbuddhyaiva mohinyā yojayitvāvṛterbalāt | 

vikṣepaśaktiḥ puruṣaṃ vikṣepayati tadguṇaiḥ || 

(Sankaracarya's Vivekachudamani 344)

The projecting power, through the aid of the veiling power, confuses a person with storms of egoistic ideas and distracts him through the attributes of that agitation. 

So the mind is so susceptible that... But this mind can be controlled only by Krishna bhakti. Yoginam api sarvesam mad-gata anantaratmana [Bg. 6.47]. Mad-gata, thinking of Krsna, antaratmana, within the core of heart. Mad gata anantaratmna, sraddhavan bhajate yo mam sa me yuktatamo matah: "He is the first-class yogi." So unless we can control the mind, we cannot become yogi. Yoga means indriya-samyamah. Yoga means not reducing fat or this or... No. Yoga means controlling the mind, controlling the senses, and concentrate it upon Visnu, Krsna. Mat para. Yogam yunjan mad-asrayah. That is yoga. When we take shelter of Sri Krishna and practice yoga, then it will be successful, not that transcendental meditation, this, all foolish things. No. So we have to control the mind. If you want liberation from this material world, you have to control your mind. Therefore Ambarisa Maharaja, he showed us an example that sa vai manah krsna padaravindayor vacamsi vaikuntha-gunanuvarnane [SB 9.4.18]. Simply engage your mind thinking of Vasudeva and talk about him. Then this agitation will not disturb you.