The Doctrine of Salvation is based on preservation rather than perseverance (Jude 1:1). The Bible proves over and over again that humans cannot save themselves, or indeed aid his salvation. The status of a man or woman who is saved is not one of precariousness like sitting on a cliff edge, but one safe in the arms of the Father; we need to do nothing, nor indeed can we do anything, to ensure our safety, for humans are too weak and sinful to be able to aid the Father in this.

To be saved we only have to believe in the Lord Jesus Christ the Son Of God.

He who believes in Him is not condemned; but he who does not believe is condemned already, because he has not believed in the name of the only begotten Son of God.  John 3:18

For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life. John 3:16

[Righteousness:] It shall be imputed to us who believe in Him who raised up Jesus our Lord from the dead, who was delivered up because of our offenses, and was raised because of our justification.  Romans 4:24-25

Anyone saved cannot be unsaved — that is lost — because God is greater than all

My sheep hear My voice, and I know them, and they follow Me. And I give them eternal life, and they shall never perish; neither shall anyone snatch them out of My hand. My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of My Father's hand. John 10:27-29

Most assuredly, I say to you, he who hears My word and believes in Him who sent Me has everlasting life, and shall not come into judgment, but has passed from death into life. John 5:24

Now He who has prepared us for this very thing is God, who also has given us the Spirit as a guarantee. 2 Corinthians 5:5

We are preserved for Him

And the Lord will deliver me from every evil work and preserve me for His heavenly kingdom. To Him be glory forever and ever. Amen! 2 Timothy 4:18

The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance. 2 Peter 3:9

What about if we sin — God is faithful to save us!

If we are faithless, He remains faithful; He cannot deny Himself. 2 Timothy 2:13

Being confident of this very thing, that He who has begun a good work in you will complete it until the day of Jesus Christ; Philippians 1:6

Paul was confidence of his salvation

For I [Paul] am persuaded that neither death nor life, nor angels nor principalities nor powers, nor things present nor things to come, nor height nor depth, nor any other created thing, shall be able to separate us from the love of God which is in Christ Jesus our Lord. Romans 8:38-39

For this reason I [Paul] also suffer these things; nevertheless I am not ashamed, for I know whom I have believed and am persuaded that He is able to keep what I have committed to Him until that Day. 2 Timothy 1:12

Salvation is by God only: we cannot aid our own salvation

For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast. Ephesians 2:8-9

 The saved will be taken into God's presence: heaven

Blessed be the God and Father of our Lord Jesus Christ, who according to His abundant mercy has begotten us again to a living hope through the resurrection of Jesus Christ from the dead, to an inheritance incorruptible and undefiled and that does not fade away, reserved in heaven for you, who are kept by the power of God through faith for salvation ready to be revealed in the last time. 1 Peter 1:3-5