yato yato niscalati
manas cancalam asthiram
tatas tato niyamyaitad
atmany eva vasam nayet
yatah—whatever; yatah—wherever; niscalati—verily agitated; manah—the mind; cancalam—flickering; asthiram—unsteady; tatah—from there; tatah—and thereafter; niyamya—regulating; etat—this; atmani—in the self; eva—certainly; vasam—control; nayet—must bring in.
From whatever and wherever the mind wanders due to its flickering and unsteady nature, one must certainly withdraw it and bring it back under the control of the Self.
The nature of the mind is flickering and unsteady. But a self-realized yogi has to control the mind; the mind should not control him. One who controls the mind (and therefore the senses as well) is called gosvami, or svami, and one who is controlled by the mind is called godasa, or the servant of the senses. A gosvami knows the standard of sense happiness. In transcendental sense happiness, the senses are engaged in the service of Hrsikesa or the supreme owner of the senses—Krsna. Serving Krsna with purified senses is called Krsna consciousness. That is the way of bringing the senses under full control. What is more, that is the highest perfection of yoga practice.
Link to this page: http://prabhupadabooks.com/bg/6/26