I don't think it is unusual for someone to use language like "personal demons" to refer to problems. I have heard it used - just not by the two therapists I hire. I have read such language in their books and blogs and such. It is a bit over the top language for my personal taste - but I don't think it gives anything too much power - I have never thought of it as being that big of a deal. More just a bit of overstatement or hyperbole is how I see it.