Why is it necessary to do sadhana daily?

Question - Gurudev, why is it necessary to do sadhana daily? 

Gurudev Sri Sri - When we say, "Do your sadhana," it means sadhana needs to be done daily. This is because there are millions of cells in our brain. Some work today, and others work tomorrow just like workers take shifts in a factory. The factory is running continually, but the workers have shifts - they come, work and leave. Similarly, in our brain, neurons work in shifts. There are millions of neurons in your brain. For them to gain knowledge, all the neurons need to be trained.