We spend most of our time walking in the light (understanding) of the old man even after we have been born from above. The Light we should see is Christ. We should be walking in the understanding of Him and our relationship to him. As Paul writes to the believers in Ephesians 2, "we are made alive with Him." "We are raised with Him." We are seated with Him in heavenly places." This should be the understanding that begins to effect our living in the earth. This is what Paul is talking about in Galatians 2.
Galatians 2:20 "I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me."