Everyone who believes that Jesus is the Christ has become a child of God. And everyone who loves the Father loves his children, too. We know we love God’s children if we love God and obey his commandments. Loving God means keeping his commandments, and his commandments are not burdensome. For every child of God defeats this evil world, and we achieve this victory through our faith. And who can win this battle against the world? Only those who believe that Jesus is the Son of God.
John is writing to his community that real and constant hope is found in faith, not in the empty promises of this world. The final verses above recall verses from John's gospel:
"I have told you all this so that you may have peace in me. Here on earth you will have many trials and sorrows. But take heart, because I have overcome the world.” - John 16:33-34
Jesus never promised that following him would be easy. As a matter of fact, here he promises that it will be difficult. The way I memorized this verse was to be reminded of those two promises. In this world you will have trouble (Duh!). AND Take heart, I have conquered this world so that you might have peace.
As the old hymn says, The strife is Over, the Battle won! Jesus has already conquered the threats of this world (sin and death), and therefore our faith in him provides us victory.