Have you ever wondered why there is a mouse seated at the feet of Lord Ganesh? It must be such a huge contradiction to find such two unlike beings together; one is powerful and pot-bellied while the other one is meek and small. In the realm of cosmic symbolism, there are certainly no coincidences. The mouse, also known as Mooshak, is in fact Ganesh’s vehicle. There are different stories pertaining to Mooshak’s subservience to Ganesh but one of the most popular is as follows.
It so happened that a demon named Gajamugasuran underwent intense penance and meditation. Pleased with his efforts, Lord Shiva gave him a boon whereby he would not be killed by any tool or weapon which has been created by people or gods. Gajamugasuran became extremely powerful and arrogant and started wreaking havoc, terrorising gods and ascetics alike. In distress, the gods went to plead with Lord Shiva to put an end to the demon’s wrongdoings. Smiling, Lord Shiva decided to send his son Ganesh to teach a lesson to Gajamugasuran. 
So, off he went and the battle started. Nothing seemed to annihilate Gajamugasuran due to his boon. It was then that Ganesh broke his tusk in an attempt to defeat the demon. Realising that he was in danger, the latter changed into a mouse in order to trick Ganesh. In his new form, he pounced on him but Ganesh proved to be too quick for him. Without losing time, he jumped on the mouse and sat on top of him. The demon struggled with the considerable weight of Ganesh until he realised that he was defeated. Eventually, he realised that his conceit had led to his downfall and he was about to be crushed to death. Humbled, he pleaded for forgiveness and offered his services to Ganesh to serve as his vehicle. Thus, the repentant demon turned into Mooshak and has been a faithful companion to Ganesh ever since.
What we can gauge from this tale is that having an over-inflated ego is the path towards one’s doom. Everything is ephemeral in life and humans as mere mortals, are going to leave material things behind upon completing their life cycle on earth. It is totally pointless to continue with the attachment to materialism to the point of turning into corrupted entities. Is that a life worth living? Therefore, let us learn to tame our ego and harness our energy for the spiritual upliftment of humankind.