I have had a few thoughts personally on these things...this statement has really evoked something.
There is, it appears, a covering placed on all of us. All of God's human creation has this covering, and you might call it "our authority" over the spirit realm, even though we are below it. It seems that this covering, similar to our health, can be destroyed and degraded (moth eaten...). Sin appears to be the direct cause of this effect, and the more abhorrent and definite, such as satanic worship, work directly against this covering, seeking to destroy it. I cannot define this cover but by a "feeling" I get, and I am sure we all rest in knowledge of it.
We are currently, this very second, surrounded by forces of might far greater than ourselves, but there is something dividing us, keeping us from their grasp: I like to call it "choice," but I believe it extends far beyond that, where our covering actually has spiritual substance. Do not leave your covering; God has commanded us not to sin for a good reason, and it reaches into the realm of personal spiritual health. So why do we not run in fear of these unseen giants which encompass us? Because we have a covering. WE ARE COVERED, Praise God, we are covered, THERE'S POWER IN THE BLOOD. As parents, it is imperitive we pray for our children and their covering, for they encounter things daily which seek to kill, rob, destroy. SO DO WE.
I believe that such "possession" may be related to this covering, and our opting out of it at some time and place. Any thoughts on this?