This body of reflection that Jesus lived in as a man is the body that was destroyed on the cross. When He was resurrected He received a new, glorious body that no longer had to live under the restrictions of a mirror. He could then freely act as a source of life, not just a reflector of life. (see Romans 6:4-11)
The same is true in our experience in various aspects but not totally. When we are born again we receive into ourselves the birth of Jesus into our heart. So long as He dwells inside of us we, in a way, can be a source of life. But at the same time we are still only reflectors of light because we have to focus ourselves on Him to have any light at all. We must follow His example of living by reflecting the light of His Father so that His life was full of that reflected light.
But the Jesus that is incarnated within us is not the pre-resurrection Jesus that only lived as a reflector but is the resurrected Jesus with unlimited power to save. The first body of Jesus is an example of how we are to live in relationship to the second body of Jesus dwelling in our heart. Maybe it is like we are a step behind Him.
At the Second Coming we too shall lose our earthly body with many of its restrictions and will receive a body like the new body of Jesus. We will then have much greater capacity for light, both receiving and giving. But even then we will never be an independent source of light apart from connection with God. Instead, God will make us an integrated part of the body of His Son – the body of Christ. In that relationship we will be as close to being like God as is possible. We will be the bodily means by which God displays Himself, His light and glory, to all the stunned and marveling universe for the rest of eternity.
We arrive at that amazing end by starting where we are now as mirrors choosing to habitually turn our attention to the original Source of light and becoming channels of that light to others. We surrender our independence and self-dependence and keep our mind stayed on Him. The result is living in perfect peace. (Isa. 26:3) This becomes the witness that attracts others who crave that peace in their own hearts to follow our example and turn their focus on Jesus who is their more perfect example of how to live as a human mirror. The more consistently we all keep our mirror focused on Jesus and the Father instead of on each other, the more perfectly His character is reproduced and reflected in our lives.