The fifth step has to do with the safekeeping of your soul. Before you are saved, you are the keeper of your own soul, and you cannot do anything but fail in its keeping. But when you get saved, you turn your soul over to the protection of another--God.

In 2 Timothy 1:12For the which cause I 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 that which I have committed unto him against that day.
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For the which cause I 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 that which I have committed unto him against that day.

In salvation, you gave up control of your own soul, and turned its safe keeping over to God the Father. God is now committed to the keeping of your soul to the end.

1 Corinthians 1:8Who shall also confirm you unto the end, that ye may be blameless in the day of our Lord Jesus Christ.
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Who shall also confirm you unto the end, that ye may be blameless in the day of our Lord Jesus Christ.

Also read Philippians 1:6For, lo, I raise up the Chaldeans, that bitter and hasty nation, which shall march through the breadth of the land, to possess the dwellingplaces that are not their's.
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Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:

Your confirmation unto the end and the performance of the work in you until the day of Jesus Christ is in the hand of the Lord.

Therefore, you cannot become lost by failing in your commitment to Christ. Since your salvation is based on the commitment of God, the loss of personal commitment would not affect your eternal destiny. No, the only way to lose your salvation is to somehow get God to fail in His commitment. This completes step five.