If you believe you can lose your salvation after being saved (born-again), you were never saved to begin with.

In The Babylonian Captivity of the Church, Luther wrote, "Even if he [the saint] wants to, he cannot lose his salvation, however much he sin, unless he will not believe. For no sin can condemn him save unbelief alone. All other sins—so long as the faith in God’s promise made in baptism returns or remains—all other sins, I say, are immediately blotted out through that same faith, or rather through the truth of God, because He cannot deny Himself."

Luther never gave his life to be kept so that John 10.28 can be said those who are born-again "they shall never perish."

It's quite weird because Martin Luther was a Calvinist which contradicts his non-OSAS stance.

Regarding God's desire for all men to be saved, Luther himself objects. In response to the claim that 'God desires all men to be saved,' and that 'Christ died for all men,' he writes that: "These points and others like them can be refuted as easily as the first one. For these verses must always be understood as pertaining to the elect only, as the apostle says in 2 Tim. 2:10 'everything for the sake of the elect.' For in an absolute sense Christ did not die for all, because he says: 'This is my blood which is poured out for you' and 'for many' - He does not say: for all - 'for the forgiveness of sins' (Mark 14:24, Matt. 26:28)"[57]

https://www.monergism.com/thethresho...le_luther.html

I don't want to dare lose this article that proves Luther was a Calvinist.

Luther-predestination.pdf