You are correct, but the Bible uses Judas as an example of one who rejected Truth in spite the witness of Truth under his very eyes.
Jesus said of Judas, one of you is a “devil”. All types of religious people name the name of Christ and are deceived because they do not possess, they only possess. Judas was condemned to hell for the very same reason all people are for unbelief.
John 6:70-71 70 Jesus answered them, “Did I Myself not choose you, the twelve, and yet one of you is a devil?” 71 Now He meant Judas the son of Simon Iscariot, for he, one of the twelve, was going to betray Him."
As far as losing your salvation, if you drift away you were never saved.
Ephesians 2:4-10 4 But God, who is rich in mercy, because of His great love with which He loved us, 5 even
when we were dead in trespasses,
made us alive together with Christ (by grace you have been saved), 6 and
raised us up together, and **made us sit **together in the heavenly places in Christ Jesus, 7 that in the ages to come He might show the exceeding riches of His grace in His kindness toward us in Christ Jesus. 8
For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, 9 not of works, lest anyone should boast. 10 For we are His workmanship,
created in Christ Jesus for good works, which God
prepared beforehand that we should walk in them.
Did anyone catch the past tense?
Romans 8:29-30 29 For whom He
foreknew, He also
predestined to be
conformed to the image of His Son, that He might be the firstborn among many brethren. 30 Moreover whom He
predestined, these He also
called; whom He
called, these He also
justified; and whom He
justified, these He also
glorified.
Notice the past tense? Why?
1 John 2:18-19 18 Little children, it is the last hour; and as you have heard that the Antichrist is coming, even now many antichrists have come, by which we know that it is the last hour. 19
They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us.
These are the one’s that claimed the name of Christ, but it was only lip service…they did not endure because they were phony. The saved always endure because they are under the care and influence of God and therefore cannot turn away.