One can’t exist without the other, right? There is always some form of light even in total darkness! Legend of Korra perfectly illustrates this in season 2 (book 2) appropriately named “Spirits”.
Korra is the current Avatar succeeding Ang (from Avatar the Last Airbender). She has mastered three elements and needs to master others. However, things have changed since Ang was the Avatar. Modernization of the current world as shown in Republic City and bending has been commercialized for sport. This appears to take the reverence out of bending and turn it into pure entertainment. This can also be said for light and dark.
We have taken light and dark and have used it in many themes for entertainment purposes in movies, music, books etc… While not inherently bad, we would be wise to not tread down the path some Mega Churches have gone down. Making worship into rock concerts, sermons into motivational speeches, etc…When this seems to be the majority of what spiritual life is about, it becomes less light and more dark in a sense.
As stated before, there is always light in the dark. That is the Holy Spirit who is always present. This is represented in the struggle between Rava and Vaatu in our Legend of Korra episode, that you can listen to here.