I have people ask me a lot if I still have demons show up or mess with me since I have been a Christian. I respond that I used to. I don't any more. Now, I'm not saying that I don't have to deal with spiritual warfare, because I do as does everyone. The demonic simply does not show up in a 'tangible' sense anymore because I am not intimidated or impressed or even interested in them. I was a tormented soul, but now I have the peace from and of God.
What brought the change was when I realized, through God's grace, that they came seeking a 'place' in me. Was that place in me my fear, idolizing them or interest? I literally had to put a stop to any reaction to them and respond only to God and His Word. He promised that He would set me free and I needed to be free. So, I had to live according to Him. And, He is faithful!
So, whenever the demonic would seek a place in me, I would choose to deal with my fear, idolizing and interest in them according to God's Word. Can you see how important it is to know Him and His Word?