“And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;”  
Mark 16:17

He isn’t expecting you to be oppressed by demons neither does he want you confused by their antics.
“…the devil… resist stedfast in the faith, knowing that the same afflictions are accomplished in your brethren that are in the world.”  1Peter 5:8-9
“How God anointed Jesus of Nazareth with the Holy Ghost and with power: who went about… healing all that were oppressed of the devil…”  Acts 10:38
Every affliction/oppression is caused by some demon; if you know this, you would give them no place but rebuke them.
Even thoughts that are antithetical to the word of God and your walk of faith are ministered by devils and you learn to do what Jesus did:
“Then saith Jesus unto him, Get thee hence, satan… then the devil leaveth him…”  Matthew 4:10-11
“But he turned, and said unto Peter, Get thee behind me, Satan…”  Matthew 16:23
The Bible says:
“Neither give place to the devil.”  Ephesians 4:27
“…Resist the devil, and he will flee from you.”  James 4:7
If the devil will flee; his lesser associates would disappear. They are already afraid of you:
“You surely believe there is only one God. That’s fine. Even demons believe this, and it makes them shake with fear.”  James 2:19, CEV
Their fear won’t chase or stop them though, until you say something. They were afraid of Jesus- God himself, but until he rebuked them, a number of them still remained around him.
Stop suffering for nothing; cast out devils!