Being born again into Christ sets us apart to know God as our Father and live lives that are different from that of the world. Being set apart unto God means to live solely for His kingdom and His pleasure, and we cannot do that without any effort on our part. God has given us the guide on how to live lives set apart unto Him and for His glory, a life full of precious promises and benefits in the now and here after. All we need do is take courage and fight off the pressures and enticements in the world and keep our focus on God. When we do that we receive ability from Him, and only then can we truly not get in the mix with the world.
So be very courageous and steadfast to keep and do all that is written in the Book of the Law of Moses, turning not aside from it to the right hand or the left, That you may not mix with these nations that remain among you, or make mention of the names of their gods or swear by them or serve them or bow down to them. Joshua 23:6-7 (AMP)