This material world is often described as an ocean of nescience. In such an ocean, everything is agitated. The mind of a great devotee is also like an ocean or a very large lake, but there is no agitation. As stated in Bhagavad-gītā (2.41), vyavasāyātmikā buddhir ekeha kuru-nandana: those who are fixed in the service of the Lord are not agitated by anything.