[Galadriel55]

I think that a big part of Sauron's fear after the Palantir "conversation" was that he wat defeated in a battle of wills/minds by Aragorn. If being the heir of Isildur, a charismatic leader of Numenorian descent, and owner of Anduril and potentially of the Ring is not enough, this little trick does it. I imagine Sauron was seriously freaking out after a "mere mortal" beat him like that in his own field.