BG 6.24-26
Abandoning without reserve all desires born of the imagination, by the mind curbing in the aggregate of the senses on every side, Little by little let him gain tranquillity, by means of Reason controlled by steadiness; having made the mind abide in the Self, let him not think of anything. As often as the wavering and unsteady mind goeth forth, so often reining it in, let him bring it under the control of the Self.