The coconut known as Sriphala (Sri, the name of Goddess Laxmi, meaning wealth; phal is fruit) is used in the making of a Purna-Kumbha (kalash) and is also an independent object of worship. A coconut alone is also used to symbolize the Lord. The three eyes of the coconut represent the three eyes of Shiva.

The fibre covering of the dried coconut is removed except for a tuft on the top. The marks on the coconut make it look like the head of a human being. The coconut is broken, symbolizing the breaking of the ego. The juice within, representing the inner tendencies (vasanas) is offered along with the white kernel – the mind, to the Lord. By breaking the coconut, the water in it flows out.

Hence, the heart, as represented by the coconut, is covered by the fibre of desire. When we strip it of all selfish desires and offer the core, it becomes an offering to God. A mind thus purified by the touch of the Lord is used as prasada.
Whenever a work of magnitude is undertaken, it is natural for the person to feel a sense of pride. Smashing the coconut is symbolic of annihilating the ego and humbling oneself before God.