The Protestant obsession with “assurance” comes from Luther’s own neuroses.
Catholics do not live in the kind of fear you cartoonishly describe, because salvation cannot be “lost” in the manner you describe. It can only be rejected, deliberately.
The conditions for a mortal sin are: grave matter, sufficient knowledge/refection, and a free act of the will.
No one commits mortal sin unknowingly or by accident. “Salvation” cannot be misplaced like one’s glasses or car keys.
The words in Ephesians describe how GOD has committed himself to our salvation. Jesus has given his life in order to bring us the possibility of living in grace.
The words in Ephesians are NOT a description of OUR subjective psychological state.
Protestants would profit by a better understanding of how Luther’s warped, neurotic psyche led him to twist the gospel. Luther re-interpreted Scriptures describing GOD’s unshakable desire to save us into a description of SUBJECTIVE “assurance” about our salvation.
To be quite honest, I've never read much on Luther.
The understanding of eternal life is evident in reading the Word.
He who believes in the Son has eternal life, but he who does not obey the Son shall not see life, but the wrath of God abides on him. John 3:36
And as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up; that whoever believes may in Him have eternal life. John 3:14-15
Sure sounds like John was talking about an assurance of salvation.
Also, I notice how you've attempted to stray away from the topic of this thread....the immaculate conception.
Perhaps it's because you cannot scripturally defend the immaculate conception. Even rcc apologists admit they can't.