And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.

(Romans 12:2)

The New Living Translation puts it this way...

Don't copy the behavior and customs of this world, but let God transform you into a new person by changing the way you think. Then you will learn to know God's will for you, which is good and pleasing and perfect.

Followers of Christ have a way of being 'out of this world' and it's a good thing. Where the world says be self serving and look out for number one, Jesus says serve others and look out for your brother's best interest. The mindset of the world is about what you can get, but the mindset of a Christian is about what you can give. The world loves darkness but the Christian loves the Light, and the Light of the World: Jesus Christ.