There remaineth therefore a rest to the people of God. For he that is entered into his rest, he also hath ceased from his own works, as God [did] from his. Let us labour therefore to enter into that rest, lest any man fall after the same example of unbelief. 
Heb 4:9-11

The good news is that we are saved by the grace of God plus nothing. Jesus finished the work of redemption all by Himself.

Because of this fact, we need not to labor under the false notion and HEAVY BURDEN that we must be faithful and persevere until the bitter end or lose our eternal salvation. This is a WORKS philosophy.

Think about this for a moment. During one of the most critical times ever on the face of the earth, when Jesus was in the garden, the disciples were told to watch and pray. Three times Jesus came and had to wake them up and told them again to watch and pray. Now you think you can persevere in faith until the end? Really?

Those who truly believe in salvation by grace enter into the rest of God because they have ceased from working to obtain eternal salvation. They realize that Jesus did a prefect work in this regard and that there is nothing to be added to it. True rest.

It is a marvelous rest to know eternal salvation is not hinged upon our weak faith and puny and sometimes sinful efforts. Sweet rest indeed.

However. this does not mean we neglect our gospel responsibility to be obedient. We should not. But the reason we seek to be obedient is not under threat of losing our eternal life, but simply we obey because we love The Lord. As any child, we desire to please our heavenly Father. And just as with our children, the consequences of not being obedient do not affect our relationship, but can affect the fellowship.

We should pray for grace to persevere to the end, but there are no guarantees that we will. We are still sinners friends.

If we either do or do not persevere in faith and good works it has absolutely no bearing on our eternal position, which was secured by Jesus on Calvary's cross. Jesus will keep all those given to Him by God The Father and not a single one will be lost.

In fact, our text tells us that is a sample of UNBELIEF to not enter into the rest of God. So if you are working to persevere and be faithful in order to make eternal salvation a surety in your life, it is a position of unbelief. Not believing that salvation is of The Lord.