God has always been about separating light from darkness.  When Satan rebelled, God expelled him out of heaven and hurled him to earth.  Rebellion couldn't coexist in the realm of God's glory. When God created the world, he physically separated the light from darkness.  (Gen 1:3)  Now, Jesus reveals that because He is the light, anyone who follows him will not walk in darkness. 
Separation, once again.  As long as we intentionally follow Jesus, we will not be led into dark shadows where Satan lurks.

One day God will separate the sheep from the goats; the true believers of Jesus from those who rejected Him.  Until then, we live a life where we, moment by moment, chose light and reject darkness.  We are partners with God in the process of sorting one against another.  I choose things He would choose, reject things He would reject.  This spiritually inductive process happens all day long.

I choose my friends wisely.  I know that light and darkness will not live together in harmony. 

I choose how I'm going to think.  I take hold of a thought, then sort it as a 'light thought' or 'dark thought'.  Is this something Jesus would think, or Satan would think?  If it's a dark thought, I cast it aside. 

I choose suggestions from others with wisdom.  Not every piece of advice is worthy of my discipleship to Jesus.  It is characteristic of light or related to darkness. 

How well I sort out my life and separate light from darkness will depend on how well I know Jesus, His life, His Father, and the Word they gave me.  I need a grid to give definitive guidelines, to help me know righteousness from unrighteousness without second guessing myself.  Jesus makes each matter clear and His Holy Spirit tutors me as I rely on Him for discernment. 

The payoff is that as long as I sort life's issues well and stay in His circle of light, the shadows are consistently dispelled.