YIN & YANG
One extreme will always change into its opposite, so that extreme yang turns into yin and vice versa.
Yin and yang consume and support each other and are usually held in balance - as one increases, the other decreases.
The concept of yin and yang originates in ancient Chinese philosophy and metaphysics, which describes two primal opposing but complementary forces found in all things in the universe.
Yin, the darker element, is passive, dark, feminine, downward-seeking, and corresponds to the night; yang, the brighter element, is active, light, masculine, upward-seeking and corresponds to the day.
Yin and yang are complementary opposites rather than absolutes. Most forces in nature can be broken down into its respective yin and yang states, and the two are usually in movement rather than held in absolute stasis.