In this passage, we consider the dual prophecies of coming conflict and a coming Comforter.
We see the accuracy of our Lord's prophecy of the coming persecution. The fact that it came true in the lives of the apostles and the early disciples proves that Christ is the true Prophet of God.
The reality of this persecution prepares Christ's people. Christ gave this prophecy to prepare his disciples, then and now.
The source of this persecution should not surprise God's people. The enemies of God may not be atheists, but rather very religious (perhaps even in the visible church), thinking they do God a service.
The absence of persecution should not be taken for granted. Rather, in times of peace we should be thanking God and seeking all the more to please Him, preparing our hearts for opposition.
Though this conflict was prophesied and persecution truly followed, Christ also promised to send the Comforter, the Spirit of God. On the Day of Pentecost, following the resurrection of our Lord, the Holy Spirit was sent into the world to convict us, to guide us, and to glorify the Son. Only the Holy Spirit can convict and convert the enemies of God to become the saved children of God.