Oooh ... exegesis of scripture. How refreshing.
Good question. I wonder if you will get an answer? [
EDIT: Looks like you did, while I was typing MY response.]
For me, the answer is obvious:
[Eph 1:13-14 NIV]
13 And you also were included in Christ when you heard the message of truth, the gospel of your salvation. When you believed, you were marked in him with a seal, the promised Holy Spirit, 14 who is a deposit guaranteeing our inheritance until the redemption of those who are God's possession--to the praise of his glory.
The HOLY SPIRIT is our GUARANTEE of the inheritance.
[Jhn 17:12 NIV]
12 While I was with them, I protected them and kept them safe by that name you gave me. None has been lost except the one doomed to destruction so that Scripture would be fulfilled.
[Jhn 18:9 NIV]
9 This happened so that the words he had spoken would be fulfilled: "I have not lost one of those you gave me."
Jesus protects and does not loose any that the Father gives Him, including us.
[Jhn 10:25-30 NIV]
25 Jesus answered, "I did tell you, but you do not believe. The works I do in my Father's name testify about me, 26 but you do not believe because you are not my sheep. 27 My sheep listen to my voice; I know them, and they follow me. 28 I give them eternal life, and they shall never perish; no one will snatch them out of my hand. 29 My Father, who has given them to me, is greater than all; no one can snatch them out of my Father's hand. 30 I and the Father are one."
We are sheltered between the hand of God the father and the hand of God the Son. It is not a position that one can fall out from.
[Jhn 6:44 NIV]
44 "No one can come to me unless the Father who sent me draws them, and I will raise them up at the last day.
Jesus is not a liar and will make good on his promise to raise those that the father has drawn to Him on the last day ... not just some of those that the Father has drawn.
Hence, I do not believe in "Once Saved Always Saved" (Implying one can be saved and yield no fruit of a changed life), but I do believe in "Perseverance of the Saints" which means ...
"he who began a good work in you will carry it on to completion" [Phil 1:6 NIV] because
"we are God’s handiwork, created in Christ Jesus to do good works, which God prepared in advance for us to do." [Eph 2:10 NIV].
Soli Deo gloria.