1 Cor 13:12
For now we see in a mirror dimly, but then face to face. Now I know in part; then I shall know fully, even as I have been fully known.
The mirror is relatively impolite gadget because it shows us how we are, not what we would like to be. The mirror reflects who we are and that's all, but there is a gospel mirror that shows us much more. This mirror reveals not only what we look like on the outside, but also what is inside. At first it's not a pretty picture! It reveals our true state and reality that we previously didn't even know existed, and not only that, but it allows us to see behind the mirror to the other side.
When it comes to spiritual things we are really in the dark. There is a veil between the natural man and God. This veil prevents us from seeing aright, whether it is God himself, us or others. A natural man is a blind man that only someone from outside can remove the veil. This is not a rival matter but very costly and concerns man’s eternal future. Natural, that is, a fallen man has no ability to sense eternal things, but only by feeling vaguely the need for something more; the eternal soul finds no fulfillment in perishable things but only in those that will last.
How can you get that new ability to see another side, which is invisible to the natural man, to see even eternity and God’s purpose for your life?
Even in this natural world we need light to see, but there is a greater and brighter light that the natural man cannot see at all, he cannot perceive it by natural means, it is beyond the reach of his vision. What is the great light that gives light to mankind.
THE LIGHT OF THE GOSPEL IS THE GLORY OF CHRIST
2 Kor 4:3-4
3 And even if our gospel is veiled, it is veiled to those who are perishing. 4 In their case the god of this world has blinded the minds of the unbelievers, to keep them from seeing the light of the gospel of the glory of Christ, who is the image of God.
The light of the Gospel is what we humans need every day! It is a light that not only reveals the path we can take, but it also reveals:
But who is this amazing "outsider" who can remove the barrier to see what is behind that curtain that hangs between perishable and eternal life? Who can give us the kind of vision that enables us to receive that transforming light?
2 Cor 3:12-18
12 Since we have such a hope, we are very bold, 13 not like Moses, who would put a veil over his face so that the Israelites might not gaze at the outcome of what was being brought to an end. 14 But their minds were hardened. For to this day, when they read the old covenant, that same veil remains unlifted, because only through Christ is it taken away. 15 Yes, to this day whenever Moses is read a veil lies over their hearts. 16 But when one turns to the Lord, the veil is removed. 17 Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. 18 And we all, with unveiled face, beholding the glory of the Lord, are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit.
If there is a key that opens all the doors in the world, would you want it? What about the key that opens the doors to eternal life (some people picture that eternal life is just a continuation of living here in a broken world. That is not what the eternal life is about.)? “But when one turns to the Lord, the veil is removed.” This is the Gospel = the Lord Jesus Christ, who has the keys of life and death (Rev.1:17-18). Our eyes are not accustomed to this brightness of the gospel that shines through that veil. We don't have what it takes to receive that ray of light that can transform us into something new. We need help!
Martin Luther said:
This the natural man cannot see: but the spiritual man only discerns the person from the Word, the veil of God from God Himself. Now this veil of God is every creature. Moreover, God here in this life deals not with us face to face, but veiled and shadowed from us; that is, as Paul saith in another place: “We see him now through a glass darkly: but then face to face” (1 Cor. 13:12). 
“But when one turns to the Lord, the veil is removed.”
This turning to the Lord is the answer. Christ said: “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.” Mark 1:15
This repentance means that you TURN to Jesus, you confess your separation from the holy and good God, that you have gone in the opposite direction against God and now you turn to Him. In short, you confess that you are a sinner – that you have completely missed the mark and lived outside of God's will. This U-turn begins a process of change that you never knew or could imagine. It opens your eyes to see beyond the veil, beyond what the human eye or mind can comprehend. The veil is removed by your Creator Himself!
18 And we all, with unveiled face, beholding the glory of the Lord, are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit.
This change does not happen just once, when you first turn to the Lord Jesus. But it will continue as long as you look at the glory of the Lord, Jesus Christ. And how do you do that? Often a first reaction is that a natural person tries to clean up his life and make him a religious person, showing some interest in godly things, but repentance is not about a person's own power to change or becoming a religious.
A real Gospel change happens by deepening your understanding of the Gospel and applying it to your daily life. But you might say, I've tried. True, many of us believers have experienced this, for too often we turn back to the ways of the natural man and turn away from the Gospel to man-made beliefs. This happens so easily, instead of looking to the grace of Christ we put our hope and faith into our own performance, good or bad. We judge ourselves by our performance and try to fulfill the faith of Christ by our own efforts, in doing so we actually reject the grace of Christ and tire ourselves with useless religious performances and ceremonies. This is how we build the religion and self-righteousness of fallen man, which is an abomination to God and a trap of pride for us.
Paul is saying here that we should have UNCOVERED faces, nothing between Christ and us! It is amazing that we are allowed to see the glory of the Son of God and even that holy God enables us to do so. When we are exposed, it means that we are completely naked before the Lord, no pretense, no cover up, nothing to hide behind, bare souls before the Lord Almighty and the King of Kings, UNCOVERED! In that nakedness we can see and turn to Christ, who has the power to transform our broken images into His likeness, from glory to glory, from good to better. This is our ongoing sanctification done by the Holy Spirit. Enjoy!
One more question remains. Why would Jesus do that? What makes Him the holder of the key of life and death or how can He change broken people and make them new creations? Good that you asked because firstly He has shown that He lived a perfect life and met all the requirements that we humans could not meet due to our sinful nature, secondly He suffered and took the burden of death for us and thirdly He rose from the dead on the third day which shows, that He defeated the last enemy, which is death. That’s why He can do that! He is the Lord of lords and the King of kings.
A man recently said to me after hearing this, "It's not fair, I have to be responsible for my own mistakes." He is right and wrong. Yes, you are responsible for your life, but neither you nor any man can undo the punishment you face. Only God Himself, Christ Jesus can, is worthy, is so loving that He came for you and took that punishment upon Himself. That's why HE IS GOOD NEWS!
Let's look daily to Him who already knows you completely and the sufferings you are going through in this broken world. He is the Gospel = good news, His all-encompassing love shines through the veil that separates us from eternity, look to Him.
“The gospel is not a doctrine of the tongue, but of life. It cannot be grasped by reason and memory only, but it is fully understood when it possesses the whole soul and penetrates to the inner recesses of the heart.”
― John Calvin, Golden Booklet of the True Christian Life
 Martin Luther, Commentary on Galatians (Oak Harbor, WA: Logos Research Systems, Inc., 1997), 104.