How is it to be attained? In a dozen different ways. Each temperament has its own way. But this is the general principle: get hold of the mind. The mind is like a lake, and every stone that drops into it raises waves. These waves do not let us see what we are. The full moon is reflected in the water of the lake, but the surface is so disturbed that we do not see the reflection clearly. Let it be calm. Do not let nature raise the wave. Keep quiet, and then after a little while she will give you up. Then we know what we are. God is there already, but the mind is so agitated, always running after the senses. You close the senses and [yet] you whirl and whirl about. Just this moment I think I am all right and I will meditate upon God, and then my mind goes to London in one minute. And if I pull it away from there, it goes to New York to think about the things I have done there in the past. These [waves] are to be stopped by the power of meditation.
- Swami Vivekananda
The Complete Works of Swami Vivekananda/Volume 4/Lectures and Discourses/The Practice of Religion