All that the Father gives me will come to me; and him who comes to me I will not cast out. John 6:37, R.S.V.
Perhaps we've gotten it from each other, this idea that God rejects us when we fail. When we disappoint each other, we know how quickly that cold distance flows in. Almost intuitively we suspect that with His very high standards God has even more reasons to reject us when we don't measure up.
In fact, some are sure that God's giving and withholding of acceptance is the leverage He uses to get us to do good. When we behave properly he rewards us with His smile. When we act selfishly, we are punished by His judgmental frown. (Somehow we overlook the fact that this never works in human relationships.)
But our God knows that the whole problem of sin is centered in our being distant from Him. He pleaded with Adam and Eve not to break the original faith relationship with Him; but they did, and---along with all their children---have been suffering the tragic losses of alienation ever since.
So the Father's plan for saving people requires that they come back to Him. In His great redemption plan He knows that we have everything to gain if He can keep us in constant fellowship with Himself. The Scriptures are full of admonition to abide in Christ. That's where the healing takes place.
What value is there, then, in His rejecting us? Having put such energy into getting us to join with Him, would He ever break the bond? Would He ever cast us out? Even using rejection as a form of leverage to get us to be good ends up in complicating the problem. Rejection always hurts, making one all the more concerned with himself and his needs. It is only loving acceptance that heals.
Furthermore, God has vastly better reasons for obedience than for us to try to earn as a favor that which He has already offered as a free gift. Obedience, which means living in harmony with His spirit and wisdom, carries all its own inherent rewards. In the same way, one who disobeys draws down all manner of terrible consequences upon his own head. Rather than needing the additional "punishment" of God's frown, he is at that point even more in need of tender nurturing.
Why, then, could Jesus say, "Him who comes to me I will not cast out"? Because He knew better than any that absolutely nothing is gained by casting one out, even when he fails.