bhagwat Geeta

यतो यतो निश्चरति मनश्चञ्चलमस्थिरम्।

ततस्ततो नियम्यैतदात्मन्येव वशं नयेत्॥

yato yato niścarati manaścañcalamasthiram |

tatastato niyamyaitadātmanyeva vaśaṁ nayet ||

Whenever the restless and unquiet mind goes forth, it should be controlled and brought into subjection in the Self. 6.26

This is what Bhagvan Sri Ramana Maharshi says. 

This is what is said in the Bhagvad Gita.