The fear of the Lord is the beggining of knowledge: fools despise wisdom and instruction. Prov.1:7
It is a terrifying thing to fall into the hands of the living God. Heb 10:31
Vengence is mine declares the Lord.
If we do not know this fear we would surly then trample underfoot the Son of God and regard as unclean the blood of the covenant by which Christ was sanctified, and insult the Spirit of Grace.
But we are to come boldly and fearlessly before the throne of Grace.
There is a difference in these two. Because we know that Christ has died for our sins and we are Children of God we can then come before the throne, Boldly to Him. But without having the fear of the Lord, we would continue to live in a manner unfitting of a Child of the King. We will Pay for the good and the bad we have done in our life, but as a Child of God we have faith and know that we will not suffer the second death.