When we come across the term "world" in the Bible, it isn't necessarily speaking of the Earth, per se. Rather, it is often speaking of a system, a mentality, or a way of thinking. This system, this mentality, is controlled by "the god of this world," also known as Satan.
A serious enemy the Christian faces today is the world. The Bible warns, "Adulterers and adulteresses! Do you not know that friendship with the world is enmity with God? Whoever therefore wants to be a friend of the world makes himself an enemy of God" (James 4:4). In the original language, the term "friendship" in this verse appears only in the New Testament and speaks of a strong emotional attachment, to love, to have an affection for, or even to kiss.
The Christian who turns from Christ and His church to seek pleasure and satisfaction from this world has put other gods in His place. That is the message God gave Jeremiah for His wayward people: "For My people have committed two evils: they have forsaken Me, the fountain of living waters, and hewn themselves cisterns—broken cisterns that can hold no water" (Jeremiah 2:13).
A cistern is a large well or pool carved in a rock. A broken cistern has sprung a leak and can't hold water. God is saying, "If you go out there to the world and drink from that well, it is not going to satisfy you."
So what are we to do when we are surrounded by this mentality, this world system that is so contrary to what the Word of God teaches? The only way to counteract this world's message is to saturate ourselves with the things of God.