Reading Notes: Seven Secrets from Hindu Calendar Art, Part C: Ardhanari's Secret and Shiva's Secret Part 1.

(Vishnu and Lakshmi)

In Hinduism, God is represented in many forms. He is best embodied in three couples: Brahma and Saraswati, Vishnu and Lakshmi, Shiva and Shakti.
Brahma: The Creator
Vishnu: The Sustainor
Shiva: The Destroyer
Lakshmi: Wealth
Saraswati: Knowledge
Shakti: Power

Since the river is always changing, one cannot step into it twice.

Shiva is known as the destroyer. He destroys desire, death, and the three worlds.  The three worlds are: our private world, our public world, and the rest. This interprets out to be that Shiva destroys our desire for life, our fear of death, and the need for the world around us. Ash is the symbol of destruction and permanence because it is created by burning things but it itself cannot be burned.

Pattanaik, Devdutt. Seven Secrets of Hindu Calendar Art. Link to videos online.