As the story goes, Lord Shiva in anger, beheaded Ganpati. After this,
Lord Brahma granted a boon that Ganesh Puja will be performed before
every puja.
Hence every auspicious or purification Vidhi requires the worship of
Lord Ganesh right at the start
At the same time, Ganapati Visarjan Vidhi teaches us the very
important concept of Samsaara i.e. the cycle of birth, death rebirth,and
that after death, every living being becomes one with nature again,
through its five elements, and is reincarnated in another form.