Besides the religious significance, the festival Diwali symbolizes the importance of element fire.
When the surrounding illuminates, there is a transmission of positive energy thus, leading to a pleasing atmosphere.
Here’s a brief on Fire:
Out of the five elements (Air, Water, Earth, Fire and Space/Sky) which make all the living entity, fire is responsible for transformation of matter from one state to other and it purifies the matter.
Fire is responsible for hunger, thirst and sleep in human body.
There are different types of fire or Agni for vision, digestion, intellect, body colour and radiance of sunlight by skin in human body.
The Indian Ayurveda principle use fire element for treatment of most of the diseases.
P.S.- Whenever you feel like you have won over negative thoughts, it’s also a day of Diwali and you can celebrate by illuminating goodness.