Notes on John 10: Apostasy?

"So the Jews gathered around him and said to him, How long will you keep us in suspense? If you are the Christ, tell us plainly. Jesus answered them, I told you, and you do not believe. The works that I do in my Father's name bear witness about me, but you do not believe because you are not part of my flock. My sheep hear my voice, and I know them, and they follow me. I give them eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father's hand. I and the Father are one."
John 10: 24-30

It says that none can be snatched out of the Father's hand. The question is whether one can choose to step out of God's hand, committing apostasy? It's an interesting point which I've been chewing over, and I'm definitely veering towards the answer "no". The verse above not only states "no one is able to snatch them out of the Father's hand" but "they will never perish". That seems quite an all-encompassing statement. It doesn't say "most will never perish". It says "they". It's all inclusive.

In any case, I just can't fathom how anyone, truly experienced in God's grace, knowledgeable of eternal Hell, with the fear of God instilled, can ever step out of the promise of infinite paradise for the momentary pleasures of this world. Something has to have gone pretty badly wrong. I guess you can argue that's pretty much what Satan did when he rebelled against God. Insane. The origins of Sin via Satan is one of the most mysterious things. How did it originate in a perfect, sinless being?