"I will give you a new heart and put a new spirit in you; I will remove from you your heart of stone and give you a heart of flesh." NIV
One of the biggest problems with Salvation is the potential for sin associated with the persistence of the self into the afterlife. As many, if not most Christians will fess up to, they still make mistakes and they still sin from time to time in one way or another. But in the afterlife, supposedly no one will sin in the Kingdom of God.
Clearly, something has to change.
God will give the Saved a new heart, and a new spirit, such that they will never stray again. But at that point, will they really be themselves anymore? Or will they simply be puppets resembling their former selves? And why not just start out that way, instead of condemning billions to the eternal junk pile as ultimate failures?
While our mistakes, errors, and failings do not, or at least should not, define us, the potential for imperfection is what helps us identify and value the best qualities and achievements within ourselves and others, what drives us toward continual improvement and mastery, and what reveals to us the true nature and need of grace and love.
As much as I hate to be wrong, I know it makes me a better person. It would be a shame to lose that facet of existence for all eternity. To err is human. :-)