Pretty much every religion I've ever seen that promised eternal salvation or, well, the Big Prize (R) has either laid out that it's within one's grasp if one is willing to do what's necessary for it. In other words, it's yours if you can just manage this. (In the minds of some, they've already by definition done what's necessary for it, even if they know what is necessary for it and haven't yet admitted to themselves that they really haven't done anything for it and are actually working quite well against it. But that's beside the point.) Things like confessions and repenting and penance are means of giving someone who has done something to screw it up another chance.
Doesn't seem to me like anyone else has picked up on that. I wonder why.