yin/yang does not equal light/dark.
Yes, this is a dualistic universe, however, love is not balanced by anything.
You can increase love, and keep increasing it.
Just like you can increase light, and increase it. Until every corner is lit.
We are speaking level 8,9... where we talk about how/why this planet was created and its starting situation. (and al the intricacies therein)
This planet was designed and set with dark and light being equal.
As of 2012, we have decided to move on as a planet of light.
It is the reason we are still here. Because if dark had one, it would have self destructed, and this was the last cycle. There was to be no more.
(Atlantis destruction was the end of a cycle, but not the end of the planet.)