John 3:7 You should not be surprised at my saying, “You must be born again.”
God wants us to live changed lives in this world so we can be seen and people who are very different from the world.
We should not be worldly people who make a difference, but different people who live in this world.
When Jesus said these words to Nicodemus (and others) He wanted him to stop and realise the difference between being in the world and being of the world.
Change! Be different! Be what God wants you to be!