How do you know when you've committed the sin unto death? If God has told you that you're going to die, does that mean you're not going to finish the race strong like all these preachers and pastors exhort people to do?
Of course all you people are going to give is opinions. So do me a favor and just post the Bible passage where God first tells Moses that He is going to die for his anger. (if you know where it is)
i know i'm opening up a can of worms here buuuut... ok.
On that same day the LORD told Moses, 49 "Go up into the Abarim Range to Mount Nebo in Moab, across from Jericho, and view Canaan, the land I am giving the Israelites as their own possession. 50 There on the mountain that you have climbed you will die and be gathered to your people, just as your brother Aaron died on Mount Hor and was gathered to his people. 51 This is because both of you broke faith with me in the presence of the Israelites at the waters of Meribah Kadesh in the Desert of Zin and because you did not uphold my holiness among the Israelites. 52 Therefore, you will see the land only from a distance; you will not enter the land I am giving to the people of Israel." - Deuteronomy 32
There's no reason Biblically to assume that we physically die for our sins now that we have Christ as our Saviour and mediator. He already died in our place! The whole point of the cross is that we no longer have to fear the wrath of God. We still physically die yes, but only because we live in a world that still feels the effects of sin (Romans 8:22). Its not a punishment against our souls though.
the sin leading to death (James 5:20) isn't talking about physical death - otherwise there'd be no warning for those who he is writing to - the scattered Jewish believers around the world.(James 1:1). death to a Christian would be a reward because we finally get to start our eternity at our Saviour's side(2 Corinthians 5:8). Damnation is considered death in a Christian context(Rev 21:8). James is most likely referring to the same thing that the author of Hebrews was:
4It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, 5who have tasted the goodness of the word of God and the powers of the coming age, 6if they fall away, to be brought back to repentance, because to their loss they are crucifying the Son of God all over again and subjecting him to public disgrace. - Hebrews 6
and really once you've gotten to that point your heart is going to be so hard against the Lord and the gospel that you're not even going to care that you've committed the sin leading to death. at least you're not going to care as long as your physical body is alive.