Perceptions, thoughts, and emotions arise in your mind as vrittis and become known to you, the eternal conscious being. To observe these changing vrittis, consciousness must necessarily be unchanging, and is therefore utterly unaffected by the vrittis it reveals — like the sun is unaffected by all it shines upon.
Swami Tadatmananda is a traditionally-trained teacher of Advaita Vedanta, meditation, and Sanskrit.