According to Hindu mythology, the practice of worshipping Lord Ganesha before initiating any ceremony holds profound significance. Shree Ganesha is worshipped to remove all the obstacles before starting any work and receive his divine and infinite blessings. Behind the ritual being followed for so many years, there is a profound tale of why all the poojas begin with Shree Ganesh. Let me recount this ancient story for you: 

Once there was a conflict going on among all the gods and goddesses about their supremacy to be worshipped first. Each one of them was proclaiming their superiority over the other. While witnessing the conflict getting more intricate, Narad Muni suggested all of them visit lord Shiva and ask him about the solution to the situation. When lord Shiva came to know about the seriousness of the situation he thought of organizing a competition for them. He asked all the deities to cover a circle of the universe. Whoever will come first will win the race and will be worshipped as supreme. Listening about the race all the deities left for taking a circle of the universe on their Vahans. 

Lord Ganesha was also part of the competition, as soon as everyone left he took a circle around Shiva & Parvati and stood in front of them joining hands. Shiva Parvati and Narad Muni were astonished to witness the act. When asked why he just took a circle around Shiv Parvati he immediately answered that parents are the universe of any child. Above all the gods in the universe, parents are said to be the superior ones. 

When all the deities came back to complete the task given to them Shiva announced Ganesha as the winner for the race. Later he also explained the reason to other gods and goddesses. Learning about the intelligence of lord Ganesha all the deities agreed and hence the conflict among them was resolved. 

This divine tale from Shivpurana explains the significance of devotion and wisdom. Thus, based on the narrative in Hindu culture lord Ganesha is worshipped before the commencing of any task or ceremony to receive the divine blessings and fruitful results.