In the science of enlightenment, we learn that the true state of joy, the natural, blissful state that is gained in awareness brings an important shift in the chemistry of the brain when it is active in the body system. When a person is in a state of bliss they are in the state of Sattvic Ananda, the state of bliss that gets activated and begins its duty of cleaning up the pitta layer of the brain.
This pitta layer that fills the brain causes one to feel tired, powerless, empty and withdrawn from life. It is this tired, pitta layer that makes a person dive deep into depression, closing the door to social engagement, healthy interaction or fruitful reflections from friends. When our mind is filled with the heat of pitta, we are unable to face life. However, through the power of Sattvic Ananda, that potential of darkness becomes non-existent.
The second thing that the quality of joy brings to the brain is awakening the Rudra, the component in our body that eats all dead cells and other decaying parts inside the body and brain system. This force comes alive when joy becomes the essence of existence. This is the important ingredient that keeps one young, energetic and blissful. As long as Rudra energy (used as the name of Shiva in the Shiva Sahasranama) is active inside of a being, they will not die, they become immortal.
Practices such as yoga, puja, kirtan and loving service are expressions of Sattvic Ananda. The more you practice these types of activities, the more they become the only useful currencies for moving and operating life. As the pitta layer slowly burns away, so do the thoughts and fears that keep one trapped in darkness. This opens one up to higher frequencies that take over the body system and eventually, guide the life into a new direction.