Everyone who penned the 66 books of the book we know today as "the Bible" knew God in a particularly unique way. That said, the inward experience that they had in their time, culture, and place transcended anything and everything that was once dominant in the world (power, culture, politics, rulers, etc.) As people came and went, God's Word remained true and still does to this day. That's one of the reasons why we read and learn from the scriptures today. In this passage, John talks about the world passing away. It was in his day, and it is even more so today. So what is John, a man who knew Jesus (walked with Him, traveled with Him, remained faithful to Him), telling the people of His day and today? Don't love the world. Readjust your priorities. Loving the world takes away time, love, focus, and so forth away from God, and God is the one who wants you to get closer to Him so that you can live a life of joy, meaning, and purpose that changes you and changes things around you. As Matthew once stated, "...seek first his kingdom and his righteousness, and all these things will be given to you as well." (Matthew 6:33 NIV). God will take care of you, but you have to care about what truly matters and not get entangled in the things of this world that pull you (and your focus on God) down.