The idea is that Jesus overcame death through the Resurrection. What that does is fail to appreciate the fact that the resurrected Christ is the crucified Christ. It's not like, 'Oh, that was just a mistake, now it's over.' Jesus continues to suffer from our sins.
Just as an athlete with natural gifts may fail to develop the fundamental skills necessary to play their sport after their talent fades, so people naturally disposed to faith may fail to develop the skills necessary to sustain them for a lifetime.