When "sin was found within him" (Ezekiel 28:15), did Lucifer get a slap on the wrist and evicted ("like lightning" Luke 10:18) from heaven? I think it was worse than that.
Wrap your mind around this: light reveals darkness ("in Thy light shall we see light" Psalm 36:9) but darkness doesn't necessarily reveal light. In other words, God's light is the only way to know what darkness truly is. "Yea, though I walk through the valley of the shadow of death, I will fear no evil, for You are with me" (Psalm 23:4). Light casts a shadow. And the only way—while walking through the valley of the shadow—that you won't be afraid, is to realize God is right there with you. Bigger than the darkness and the fear. Realize that He's leading you through it. Contrast this: Jesus says that "men (people) love darkness rather than light because their deeds are evil" (John 3:19). Those people are blind to the light—the better way. Their darkness is not revealing God's light. Else they would choose His way rather than their own (would they really?).
Manicheanism (after Manes, 3rd c. founder) teaches that dark and light are both integral to the world and a balance between the two is necessary. Harmonious. The same principle underlies the yin and yang of Chinese philosophy.
Prior to Lucifer's unmasking and fall, there was only light. Darkness has not always been and there will come a time when darkness will be no more (see Revelation 22:5). Here in the middle, however, we must deal with it: Psalm 119:130 says "the entrance of Thy word gives light, it gives understanding to the simple". God's word, the truth therein, will show us the light we need.
The only way to see light—true light, God's light—is to seek His face. Psalms says that "God is a sun" (Psalm 84:11), and that "His face doth behold the upright" (Psalm 11:7). It also says that "light is sewn for the righteous" (Psalm 97:11), meaning it'll be there when you need it.
Think about the universe. Without the light from the sun and the stars (the moon simply reflects the light from the sun onto the night), everything's black. This is stark. But spiritually, it's different. The Holy Spirit is always shining through the spiritual. Always joyful. And aligning ourselves with Him through obedience, worship and interaction (see Proverbs 3:5-6)—anything done in love—will cause His light to diffuse through the membrane separating the spiritual from the natural.
In closing, some Bible commentaries say that Lucifer (satan) was "the Prince of Persia" (Daniel 10:20). Manicheanism was heavily influenced by Ancient Zoroastrianism which originated from Persia.
"For You will light my candle: the Lord God will enlighten my darkness" (Psalm 18:28).
Do truth. Come to the light. (see John 3:21)