I was recently praying with a girl who had a demon who had attached itself (himself\herself\itself? what do you use when speaking of unseen evil fallen angels) to her. She was fearful that she was possessed by a demon because whenever she prayed for deep inner cleansing from the Lord...something that felt like it was deep within her resisted her prayer. She felt something physically and felt as if she needed to vomit. No one had pre-conditioned her to expect this...it's just that she felt it. When this happened she would become fearful and stop praying. She came to me asking, "Am I demon possessed?"
Knowing her genuine commitment to Jesus Christ and that she was born again, I assured her, No, you certainly are not possessed". I explained that when someone is born again it means that the Spirit of God has taken up residence in the spirit and soul of person and that a demon cannot "possess" that territory any longer.
However that doesn't mean that demons can't attach themselves to our thinking, to our emotions. Paul when writing to the Ephesians told us to be very careful not to give the Devil a "foothold" (4:27). "Foothold" is a Greek word meaning "a space that is marked off from the surrounding space". In this context, we are being told to deal with our anger quickly and healthily or we will give the Devil a "marked off space in our lives", a "foothold", or a "stronghold".
When that happens we are certainly not possessed but we have allowed a place where a demon can get its talons into us. We must aggressively take that space back through confession and deliverance.
Another picture is "wrestling". Ephesians 6:12 describes demons as "wrestling" with us. When a demon takes hold of us in certain areas, it does not want to let go. It has grasped us in an aggressive wrestling hold. When we begin to exercise the authority of the name of Jesus against it, it wants to hold on and this can be a struggle. When manifestations take place (writhing on the floor, eyes rolled back, different voices coming out of a person, coughing, vomiting, supernatural strength, death appearance, hissing, drooling and many more which I have encountered) I believe these are efforts of demons to "hang on" resisting the power that is breaking their hold on an area of a persons life.
As the person confesses their sin, confesses the name of Jesus, confesses the defeat of the Devil and his demons through the blood of Jesus and Word of God, the demon must give up that foothold, it must release its wrestling hold on the person.
This young lady met us for prayer, actively engaged the area of demonic stronghold, and agreed with us as we prayed for breaking the hold of the enemy. There were some violent manifestations that could only be attributed to a demon reluctant to release his territory. But after a short while of prayer, the demon left and she felt a tremendous release. She was glowing even several days later. She testified to the difference that she felt in her life. Praise to the one who "ALWAYS give us the victory".