Questions addressed in this passage:
How do we receive reassurance that we are from the truth? That is, can we give examples of how God's love is demonstrated through our actions?
Believing in Jesus Christ and loving one another. Have we tried to do the first without doing the second? It's one command, not two.
How do we know that Jesus abides in us? We know because we are obeying his commands.
John Wesley preached against what he called the "Almost Christian." The Almost Christian does nothing that the Bible forbids. He avoids murder, theft, adultery, and fornication. He keeps the Sabbath. He does to church, he prays, and so on. But, according to Wesley, he is missing something necessary. He's missing the command to love his neighbor a himself.
How do we become the "Altogether Christian"? We love God and those whom God love--including people we don't even like. After all, this is his commandment:
that we should believe in the name of his Son Jesus Christ and love one another.