Your names are written in the lamb's book of life from the foundation of the world.
One way to know that is true is Hebrews 4 says, God rested from all His works on the 7th day.
And also mentions those who will not enter His rest.
Hebrews 3 says people can not enter in because of UNBELIEF.
12 Beware, brethren, lest there be in any of you an evil heart of unbelief in departing from the living God; 13 but exhort one another daily, while it is called “Today,” lest any of you be hardened through the deceitfulness of sin. 14 For we have become partakers of Christ if we hold the beginning of our confidence steadfast to the end, 15 while it is said:
“Today, if you will hear His voice,
Do not harden your hearts as in the rebellion.”
Failure of the Wilderness Wanderers
16 For who, having heard, rebelled? Indeed, was it not all who came out of Egypt, led by Moses? 17 Now with whom was He angry forty years? Was it not with those who sinned, whose corpses fell in the wilderness? 18 And to whom did He swear that they would not enter His rest, but to those who did not obey? 19 So we see that they could not enter in because of unbelief.
Hebrews 4 makes the point, God rested from all His works on the 7th day, and that would include all those names who are written in the book of life of the Lamb who are reserved for salvation by Him in the last time.
People enter into God's rest because of their belief in Christ. An evil heart of unbelief departs from God, Hebrews warns them in the church to not depart as they will not be saved if they do, which of course to us is obvious, that only those who have faith in God through Christ are saved. God keeps us by the power of God through faith, meaning His power is manifested to us by our faith in Him which is given to us by His grace.
Hebrews was written to Hebrew believers in Christ and the book is exhorting them to remain in Christ and the excellency of the NC versus the OC. And that there is no going back to OC ways with God, there is no grace left in the OC faith, it has been superseded by the new. No turning back is possible.
Hebrews 4 New King James Version (NKJV)
The Promise of Rest
4 Therefore, since a promise remains of entering His rest, let us fear lest any of you seem to have come short of it. 2 For indeed the gospel was preached to us as well as to them; but the word which they heard did not profit them, not being mixed with faith in those who heard it. 3 For we who have believed do enter that rest, as He has said:
“So I swore in My wrath,
‘They shall not enter My rest,’ ”
although the works were finished from the foundation of the world. 4 For He has spoken in a certain place of the seventh day in this way: “And God rested on the seventh day from all His works”; 5 and again in this place: “They shall not enter My rest.”
6 Since therefore it remains that some must enter it, and those to whom it was first preached did not enter because of disobedience, 7 again He designates a certain day, saying in David, “Today,” after such a long time, as it has been said:
“Today, if you will hear His voice,
Do not harden your hearts.”
8 For if Joshua had given them rest, then He would not afterward have spoken of another day.
9 There remains therefore a rest for the people of God.
10 For he who has entered His rest has himself also ceased from his works as God did from His.