When my wife and I started training as foster parents four years ago, one of the things we were told was,

"This is a completely different kind of parenting.  On the surface, it is the same--the basic nurturing, caring, feeding, and clothing but you need to be aware that behaviours are going to be more intense.  Your friends and family who are not parents from the foster-care system will not understand the challenges you are going to be working through.  You will hear things like, "oh, that's just what kids do" when you try and explain some kind of defiant act your kid is engaged in.  They won't comprehend how intense these behaviours are because they have no base-line from which to gauge."