My dear friend Jean Skaggs, who deals with this often says…
When the dog is guarding you...get up and leave the area.
Don't squirt the dog, don't say anything, get up and leave.
Turn your back and ignore.
These dogs do get it.
You might makes many trips off the couch, when that is where you are...
But they will get it.
I would be happy to send you to her if you have more issues.
But really, its just that simple...