|Chapter 2: Contents of the Gita Summarized|
indriyanam hi caratam
yan mano 'nuvidhiyate
tad asya harati prajnam
vayur navam ivambhasi
As a strong wind sweeps away a boat on the water, even one of the roaming senses on which the mind focuses can carry away a man's intelligence.
Krishna use a fitting analogy to explain what happens to a person unable to control his senses. Where the senses go, the mind follows and where the mind goes, so does the intelligence. A strong wind can only sweep away a boat not anchored. Similarly an mind that is not anchored in sense-control will simply roam far and wide in a frustrating quest for satisfaction.
Please read the Sanskrit Verse and the Prabhupada's Purport.