Everything in life to be sustained has to go in circle, everything has to be interchanged between two opposites.
If plants only produce oxygen by using carbon dioxid and there is no1 to convert it back to carbon dioxid by breathing. Planet would have too much oxygen and no carbon dioxid, we wouldn't exist.
If organisms on this planet live forever and no1 is dying, our biological material couldn't be degraded by microorganisms and there would be no enough chemical elements for plants and other microorganisms, so we woudn't exist.
IF there is no price dropping in crypto market cap, we could not have price rising neither.
So as we can see we need negativity to insure existence of positivity and vice versa .
Every day we have exchange of day and night, if there is no resting period there wouldn't be active period.
Each part of the day has its own charms and beauties, which you like more?
And the biggest contrast in the world is between man and woman!
But still every pigeon needs a dove.