I'm not sure what you mean by the above underlined by me.One difference between Catholic and Protestants is that Protestants tend to think in all or nothing terms.
Catholics think in terms of growth (and I suppose decline).
Mortal sin totally breaks our relationship with God and total loss of grace.
But venial sin damages our relationship with God and we lose some grace from our souls.
(We see santifying grace as a quality of the soul).
Another important difference (as I understand it) is that Protestants tend to see this in legal and behavioural terms whilst Catholic thinking is in real terms. So when we are justified we are made righteous. Protestants see this in legal and behaviousral terms but in Catholic thinking righteousness is a real quality of the soul. It can grow and decline. Thus justification can grow and decline.
Regarding Sanctification, think of it as holiness. We can grow in holiness and become less holy.
It's a complicated subject. I think what I have written is correct Catholic thinking but I may not have got it quite right.
I'd say that Protestants do see justification in a legal sense, but only in the sense that God DECLARES one to be righteous. I think this is what you call real terms (not sure). When we are justified we are made righteous. This is a real quality of the soul. It can grow and sometimes decline...Protestants call this backsliding...if a person stops backsliding, they are still saved, if they continue to live in sin then it is possible to lose salvation.
Of course there are some Protestants that do not believe one could ever become lost after "accepting Jesus"...I believe the major denominations do not believe in eternal security but in conditional security...security that is conditional on reamining in christ, as Jesus says in John 15:5.