Life is a series of battles against the world. Left to our own devices, we usually end up losing the battles: against the temptation to eat too much, against the temptation to be lazy, against the temptation to make the easy choice instead of the right one, against the temptation to be cowardly rather than courageous. But we can win instead of losing if we draw on a power that is greater than ourselves. In chapter 5 of his first letter, John says:
Everyone who believes that Jesus is the Christ has been born of God. Everyone who loves the parent also loves the child. We know that we love the children of God when we love God and obey his commandments. Loving God means obeying his commandments, and his commandments are not oppressive. Anyone who is a child of God defeats the world. Our faith is the victory that has defeated the world. Who is it that defeats the world? It is someone who believes that Jesus is the Son of God.
The person who has faith in Jesus enlists Jesus to fight the battles on his or her behalf. Jesus has already overcome the world through his victory over death and sin on the cross, so that when we enlist Jesus to fight on our behalf we cannot lose. We make be weak, fragile, cowardly, lazy and susceptible to temptation without Jesus, but when Jesus is in control victory over the world is guaranteed.