Jesus delivered this man with the unclean spirit. Jesus has that authority today. He can deliver us from whatever may get into us. It is sad that so many people even in the church only give lip service to the authority of Jesus. They really don't believe that he can deliver them.
There is an old story about some linemen who were busy putting up telephone poles through a farmer's fields. The farmer ordered them off his land, whereupon they showed him a paper giving them the right to plant poles wherever they pleased. Not long afterward a big and vicious bull charged the linemen. The old farmer sat on a nearby fence and yelled: "Show him yer papers, darn ye, show him yer papers!"
For to many Christians, Jesus' authority is only a paper authority. It is something we study for inspiration, but we really don't believe it applies to our situation. Is this our belief? There are too many witnesses to Christ's authority today for this position to be true!