Since Jesus is the light of the world He shines through a person who loves Him and and everyone sees that light in the person's life. If there is no love of Jesus in the person all the world sees is darkness because of the sin.
I really like that. It's sort of the same view I have. If Jesus lives in us, then we see life as He does with compassion, mercy, and love - because He is the Light within us, not darkness. It reminds of John 3...
17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.