Without self-control, attention becomes drift.

The simile offered here — of a boat blown off course by wind on water — beautifully captures the dynamics of how wisdom is lost. A ship properly navigating the waters has a course, a destination, a helmsman. But when a powerful gust seizes it, all of that purposeful direction is immediately overridden by the force of nature. The ship goes where the wind wills, not where the navigator intended.

In the same way, when the mind 'anuvidhīyate' — slavishly follows after — any one of the senses that is roaming among sense objects, the person's entire accumulated wisdom is swept away in an instant. This is why spiritual progress can seem so fragile: years of practice and clarity can apparently be undone by a single moment of giving in to a compelling sensory pull.

The word 'harati' (carries away, steals) suggests violence and suddenness — this is not a gradual erosion but an abrupt hijacking.

The verse also implies the remedy through its metaphor: a well-anchored boat, or one with a strong helmsman at the wheel, is not easily overturned by gusts. The anchor is the practice of buddhi yoga; the helmsman is the discriminating intelligence that has been trained to recognize the difference between awareness and its objects.

The Gita's emphasis on constant practice and detachment is precisely the training that builds this capacity for one's wisdom to remain stable even when the senses are active.