Jesus doesn't want us out of this world; He wants the devil out of us. He doesn't ask His Father that we be kept people: kept from the ills that touch everyone's life. After all, "He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous" (Matthew 5:45). So if we enjoy the positives in life, we will also have to endure the negatives. Even Job, in the midst of every negative possible in his life, said to his aggrieved and complaining wife, "Shall we accept good from God, and not trouble?" (Job 2:10).
Just because we are Christians doesn't mean we are to be spared sorrows and suffering. Jesus prays that we will be protected from sin, the greatest evil of all. Edward Taylor wrote, "My sin is red: I'm under God's arrest." Satan is colored red, and he is the person and personification of sin. But God has promised, "He who overcomes will be dressed in white" (Revelation 3:5). "Always be clothed with white" (Ecclesiastes 9:8). White garments in the East were considered symbols of joy and purity. We are under God's rest when clothed in white!
But how are we kept from the epidemic of evil? We are clothed in white by going to the stronghold, God's Word. Here is our sanctuary. The world has many disguises and disgusts, and it is only with the help of the Holy Spirit that we can discern and disengage from what hurts God and ourselves. "Get behind me, Satan! You are a stumbling block to me; you do not have in mind the things of God, but the things of men" (Matthew 16:23).
We have the mind and nature of the world, yes. But Jesus prays for us to remain in the world and yet not be a part of its offenses. A firm "Get behind me, Satan," will help us to remain a decent force for good.