The warnings against apostasy and loosing your salvation are plentiful,
Romans 11:20-22 - But they were broken off because of unbelief, and you stand by faith. Do not be arrogant, but be afraid. For if God did not spare the natural branches, he will not spare you either. Consider therefore the kindness and sternness of God: sternness to those who fell, but kindness to you, provided that you continue in his kindness. Otherwise, you also will be cut off.
Colossians 1:21-23 - Once you were alienated from God and were enemies in your minds because of your evil behavior. But now he has reconciled you by Christ’s physical body through death to present you holy in his sight, without blemish and free from accusation-if you continue in your faith, established and firm, not moved from the hope held out in the gospel. This is the gospel that you heard and that has been proclaimed to every creature under heaven, and of which I, Paul, have become a servant.
1 Timothy 1:18-20 - Timothy, my son, I give you this instruction in keeping with the prophecies once made about you, so that by following them you may fight the good fight, holding on to faith and a good conscience. Some have rejected these and so have shipwrecked their faith. Among them are Hymenaeus and Alexander, whom I have handed over to Satan to be taught not to blaspheme.
Hebrews 6:4-6 - It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age, if they fall away, to be brought back to repentance, because to their loss they are crucifying the Son of God all over again and subjecting him to public disgrace.
Hebrews 10:26-31 - If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, but only a fearful expectation of judgment and of raging fire that will consume the enemies of God. Anyone who rejected the law of Moses died without mercy on the testimony of two or three witnesses. How much more severely do you think a man deserves to be punished who has trampled the Son of God under foot, who has treated as an unholy thing the blood of the covenant that sanctified him, and who has insulted the Spirit of grace? For we know him who said, “It is mine to avenge; I will repay,” and again, “The Lord will judge his people.” It is a dreadful thing to fall into the hands of the living God
2 Peter 2:20-22 - If they have escaped the corruption of the world by knowing our Lord and Savior Jesus Christ and are again entangled in it and overcome, they are worse off at the end than they were at the beginning. It would have been better for them not to have known the way of righteousness, than to have known it and then to turn their backs on the sacred command that was passed on to them.
2 Peter 3:17 - Therefore, dear friends, since you already know this, be on your guard so that you may not be carried away by the error of lawless men and fall from your secure position.
1 John 2:24 - See that what you have heard from the beginning remains in you. If it does, you also will remain in the Son and in the Father.
Revelation 3:5 - He who overcomes will, like them, be dressed in white. I will never blot out his name from the book of life, but will acknowledge his name before my Father and his angels. (Obviously your name can be blotted out)
Revelation 22:19 - And if anyone takes words away from this book of prophecy, God will take away from him his share in the tree of life and in the holy city, which are described in this book.
In Rev it even talks about a man's name being blotted out of the Lambs book of Life, which means it had to be written in and then REMOVED.