Believe God and be Sure!

The main error of those who teach against the secure promise of everlasting life to all who believe in Jesus Christ is that it dishonors God.  I’m reasonably sure that is not their intention.  but they are basically saying Jesus Christ’s death and resurrection fail to satisfy God’s need for justice and his desire to redeem us from our bondage to sin.  They imply something was lacking in God’s redemptive plan or Jesus Christ’s sacrifice that must be made up by us.  However, I’ve never heard anyone explain what that deficit actually was.
 
That leaves their followers with no idea of what they must do to fill in the gap.  Logically, it would seem they either live in fear or surrender to a fatalistic hope for the best approach.  Most people I know that hold the view that salvation can be lost adopt the hope for the best position.  While they can’t say for sure where the line between heaven and hell is; they are pretty sure they’re on the right side of it.  God says there is no reason to live with any uncertainty.  We can have complete assurance by just taking God at His word.  We have been saved by grace through faith without any effort on our part (Ephesians 2:8 & 9).  And God does have a tract record of keeping His word!
 
For when God made a promise to Abraham, because He could swear by no one greater, He swore by Himself, saying, “Surely blessing I will bless you, and multiplying I will multiply you.” And so, after he had patiently endured, he obtained the promise.  For men indeed swear by the greater, and an oath for confirmation is for them an end of all dispute.  Thus God, determining to show more abundantly to the heirs of promise the immutability of His counsel, confirmed it by an oath, that by two immutable things, in which it is impossible for God to lie, we might have strong consolation, who have fled for refuge to lay hold of the hope set before us.  Hebrews 6:13-18