I don't know that the mental machinery is as elastic as you say. Our bodies to indeed adjust to mental stress, in fact parts of the brain that respond to fear and stress will overdevelop in relation to other areas producing aberrant behavior.

There are mental trauma, that has not been caused by physical trauma, that will end up being like the gash you describe never being able to acclimatize to.

I take your point about the use of the word scarring...I was just trying to draw a certain type of similarity into the conversation...it certainly isn't a perfect analogy.

One other thing, though...is it really a surprise that discussing mental or emotional damage would use a physical analogy? We don't culturally have a large body of language for describing things accurately that are "just in your head."