The perturbation owing to thoughts appears to rob the Self of its peace.

Ramana Maharishi:  Prana and mind arise from the same source. The source can be reached by holding the breath or tracing the mind. If you cannot do the latter the former will no doubt be helpful. Regulation of breath is gained by watching its movements. If the mind is watched thoughts cease. Peace results and it is your true nature. King Janaka said: “I have now found the robber (namely the mind) who has been robbing me of my ‘I’-ness. I will instantly kill this thief.” The perturbation owing to thoughts appears to rob the Self of its peace. The perturbation is the mind. When that ceases the mind is said to take flight. The Self remains as the undisturbed substratum.