In John 15, Jesus is saying what the hallmarks of a Christian are.

  1. We should love God, not in a sentimental shallow way but showing this love by doing what he commands. By being committed to doing his will.
  2. We should love others as Jesus loves us:

    1. We should be self-sacrificing, putting other before ourselves, “Greater love has no-one than this, that he lay down his life for his friends.” Jesus put us first when he went to the cross, if we are to imiate him, we should put others first.
    2. We should be providing for the needs of others.
    3. We should be purposeful in our love, not being do-gooders and getting in the way, but being truly useful.

Only by doing these things, by putting God and others first, can a person have real joy.

Chapter 4 of Paul’s letter to the Ephesian church tells us that Christians should be completely different from the rest of the world, not in a strange odd-ball kind of way, but in their attitude to God and the world.
Firstly, a person needs to be changed into a Christian. There’s no point in trying to be different if you’re not different. There’s no point in attempting to live a life if you don’t have life. Paul says that a Christian is a new creation, which only God can accomplish. A person’s attitudes to sin and impurity will change, as God works in them through his word. They will know God more and more as they hear his word, and God will give them true life through faith in Christ.
Secondly, a Christian will continue to have a different attitude to life, they will pursue righteousness and holiness, seeking to glorify God and in doing so, having joy everlasting.