The book of Job offers an interesting, behind-the-scenes look at what the enemy can and cannot do in the life of the believer. Although God described Job as blameless and upright, He allowed the devil to send trials and adversity into Job's life. From this story, we see that the devil, in spite of his power and wicked agenda, still has to ask permission when it comes to the child of God, because of God's hedge of protection.
In John 10:7, Jesus said, "I am the door of the sheep." A shepherd would set up an enclosure called a sheepfold, where he would keep his sheep at night. But instead of having a door on hinges to protect the sheep and to keep them in and predators out, the shepherd himself would sleep at the opening of the sheepfold. Any predators that would want to kill the sheep would have to go through the shepherd. In the same way, when the devil comes knocking at the door of the believer, he has to go through Jesus.
That's important to remember—the devil cannot do whatever he wants in the life of the Christian. He has to ask permission. The Lord gave him permission and put certain restraints on what he could do in Job's life. And although Job suffered greatly, he came through those hardships, and God blessed him even more in the end.
When we are undergoing great trials and hardships, we should remember the Lord is watching. He is still protecting us. He may allow certain temptations. He may allow certain hardships and certain difficulties. But He knows your breaking point. And every move of the enemy must first come by permission through the protective hedge of Jesus.