So you are able to UNDO what God has done.
For me, what the IMMORTAL has done can NEVER by any mortal be UNDONE.
Then He shouldn't have said what He did to Nicodemus :
Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
John 3:3
And that is why it was God Who caused our being born again:
NAS 1 Peter 1:3 Blessed be the God and Father of our Lord Jesus Christ, who according to His great mercy has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead
Man's default position is not "saved".
Man's default position at birth is "saved", being born in Christ. This condition is vividly demonstrated by our Lord in His parables of the lost sheep, lost coin, and lost son.
1. Before the sheep got lost, it was in the sheepfold under the care of its shepherd.
2. Before the coin was lost, it was with its owner.
3. Before the son went lost, he was at home with his father.
So with us all. We begin life NOT lost. And to be NOT lost is to be in Christ. But we all like sheep went astray (Isa 53:6). This is why we are all enjoined to repent (Luke 13:3,5).
The command for people to repent is the same command God issued in the old testament (Ezek 18:30); the same command God now wants all men everywhere to do (Acts 17:30); the same command Jesus made in the gospel that He preached (Mark 1:14, 15); the same gospel He wanted preached to the world before He comes again (Matt 24:14).
Repentance is the Greek "metanoia" - change of mind for that which is good. Confronted with the opportunity and about to do evil, one changes his mind and does good instead. IOW, it is overcoming evil with good (Rom 12:21).
Overcomers will Christ not blot out from the book of life and will be seated with Him in His throne even as He also overcame and sat down with the Father in His throne (Rev 3:5, 21). When Christ comes again to reward every man according to what each has done (Matt 16:27; Rev 22:12), all NOT blotted out will be allowed entry to the heavenly portals (Rev 21:27); all blotted out will have their portion in the lake of fire (Rev 20:15).