Once saved, always saved?

The Bible plainly states, "he who endures until the end, he SHALL be saved". This tells us two things. First, that he who does not endure until the end will not be saved. And second, that salvation happens at the moment of death, not before. Paul compares earthly life to a foot race we must run well if we wish to receive the prize - salvation. Obviously the prize in a race is awarded at the end of the race, not in the middle of it. The idea that one can be on this earth and be assured of salvation is just one more unbiblical Protestant tradition, one more deviation from original and true Christianity that no Christian on earth ever heard of until a few hundred years ago.