When God created light in Genesis 1:3, there was actually no darkness. It was gone because the light continuously shines down on Earth. So God had decided to separate the light and darkness to take their place at different period of time. God's work in separating light from darkness was mentioned on Genesis 1:4.
I know that it would be pretty bad if there's no light for everyone of us. But, what if there's no darkness at all? Do you think that it would be more beneficial for us?