Sometimes what's inside of men is not as pretty as what is outside of man. It is always a little painful to have these things uncovered, exposed by the light.
Consider Lucifer, the light-bearer, son of the morning. The ambition to be sole ruler of Light blinded him; and murder was created. The ambition of Cain also , toward Abel, came in an act of worship, where we partake of the light. Cain could not bear being second before God; he had to be first; and right.
This issue is at the heart of rebellion itself, and therefore the redemption; the Cross of Christ Jesus itself. Remember also that it is a walk with God, a process ; not an event to receive the light. We carry Adam's dark heart yet, right along with the illumination of the Holy One; the light of the Holy Spirit.
5. "This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all.
6. If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth:
7. But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin."
The dark is going to be with us, until the day star dawns, but if we walk in the light, and love it, the darkness must disappear.
2 Peter 1:18-20 (New International Version)
18. "We ourselves heard this voice that came from heaven when we were with him on the sacred mountain.
19. And we have the word of the prophets made more certain, and you will do well to pay attention to it, as to a light shining in a dark place, until the day dawns and the morning star rises in your hearts."
More and more as we walk along, and in full glory on that day that He returns. It, however, is a battle, and a test of whether we love light, or the dark side of creation.