From whatever cause the restless and the unsteady mind wanders away, from that let him restrain it, and bring it back under the control of the Self alone.

yatasyataḥ = wherever; niścalati = becomes verily agitated; manaḥ = the mind; cañcalaṃ = flickering; asthiraṃ = unsteady; tatastataḥ = from there; niyamya = regulating; etat = this; ātmani = in the self; eva = certainly; vaśaṃ = control; nayet = must bring under.;