Let me expand on what I mean when I say that Jesus is the fulfillment - not the replacement - of man.
First off, the statement doesn't deny the truth stated in John 12:25, but emphasizes it:
He who loves his life loses it, and he who hates his life in this world will keep it to life eternal.
Please notice, the verse doesn't claim a man's life needs to be replaced but rather it presents the irony in how his life is truly found. Likewise, the question...
For what will a man give in exchange for his soul? Mark 8:37
...refers not to the exchange of Christ's life for ours but to man's false perception that life can be gained through the acquiring of possessions in this world.
Now, while it is true that Christ has become my life he did not become ME in place of me, he became my LIFE so that I could finally BE me.
I have been crucified with Christ; and it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself up for me. Galatians 2:20
Seen as a replacement, a bogus identity conflict often rises up from which we struggle to achieve a less-me-more-Him relationship; but as a fulfillment, no such contradiction exists.
You see, without Christ, I had been loving what I only perceived as my life, which means that I had been existing in a constant state of loss regarding it. Trying to find myself in this world only succeeded in pushing my life far from me. Through Christ, the life I thought I had gained in this world was actually against me, and I have come to hate that bogus thing ... even though I might often try to convince myself otherwise!
We have labored far too long under the fallacy that we ever had any life to begin with, for all we ever had was the emptiness of a parasite attached to a dead host. That's right, we lived as vampires sucking the life-blood from others, but those sources only contained an artificial nourishment that had to be replenished on a constant basis to keep the lie alive. The activity of the exchange perpetuated the illusion that life was somehow being transferred or sustained. In reality, we were incessantly haunted by the nagging demand of emptiness, even while claiming to have been fulfilled by it.
The good news is that in his death Jesus nailed the lid shut on the vampire's coffin, for he took that former emptiness and condemned it to death in his own body. He became for us the embodiment of sin, doing away with the perversion of that which had originally been created in God's image. The former was done away with ... and we finally found ourselves.
The simple reason many Biblical statements regarding the former life often reek of contradiction and impossible demands should be obvious: they are viewed according to the false perception of life as imagined by a marred creation that has no real life! When Jesus addressed the people his words couldn't help but create conflict because he spoke of their life in terms meant to expose their false perceptions of it. Statements made after Christ's death and resurrection are likewise misread because they force those same false perceptions into the words we read even though heavily contrasted to reveal the only true life.
In Christ - who is the very image of God - the unfulfilled was fulfilled, the incomplete has been made complete. Apart from Christ, the designation "Made in God's Image" has less meaning than a faded label on an old pair of soiled underwear. Nevertheless, that fatally flawed image has been foreshadowing the real one from the beginning, even as a mirage in the desert testifies that water is not merely a dream. The image insists something substantial.
And yes, it has everything to do with the word of God. :)
One of these days I may continue this.