People usually forget the power demons have...
Demons are fallen angels... angels were practically the 2nd most powerfull beings in existance, below God.
Ever felt doubt creeping in your heart when you were about to do things?
Ever found yourself stalling things you actually want to do without any obvious reason?
These are demonic influences. They make you reconsider things, they put doubt in your heart.(Did God really say?)
Ever heard your pastor preach something that sounded right and scriptural but you felt something against it?
Demonic influence is very very subtle. The error Christians make is to think they can't be influenced.
I would say for a born again Christian it's not possible to be possesed, becouse the Holy Spirit lives in him, But if he's not carefull he can be influenced.
Therefor it's wise to pray every time you feel doubt about something that you shouldn't feel doubt over.
Be carefull about fear, doubt and unbelief... It can come from another source than yourself.
if unsure, pray, never hurts to pray(to God that is *grin*)
Michael