Mystical peace mantra of Upanishads

The following is an excerpt from a samvaad (dialogue) session with Acharya Prashant.

Questioner: Sir, Namaste! Clearly, the opening of the Upaniṣad itself is mysterious. Kindly say something.

Acharya Prashant: You can call it mystery or you can call it an exalted, bold, uninhibited expression of your deepest desire.