God does not let any of His flock stray.

"My sheep hear my voice, and I know them, and they follow me; and I give them eternal life, and they shall never perish, and no one shall snatch them out of my hand." (John 10:27-28)

This passage is about as blunt as Jesus gets: there is no power in Heaven or Earth that can separate the people of God from His love. Those who are born again in Christ are not signing up for a religion. Their basic nature has been transformed. Sin and death, while still a presence in their lives, no longer have power over them. Once they were wayward creations; now they are beloved sons and daughters of the Almighty and heirs to the Kingdom of Heaven.

So what of those who have lost their faith, or have cast it aside? What of those who turn to other religions, or reject the idea of God altogether?

"They shall never perish. No one shall snatch them out of my hand."

Our doubts and failings are not, can not, be stronger than God's love. It's easy for us to imagine a god who gives up on us when we don't listen to him, or who "doesn't give a fuck" about us at all, as VaiPhile suggests above. It's only common sense; people are like that. It is very, very hard for us to grasp the idea of someone who is willing to give everything, even to the point of torture and death, for our sake. Yet that is the nature of the God presented to us in the Bible.