Gods gift of Grace is hard to understand, becasue , this world, is a do for me and ill do for you. To just recieve something so wonderful for nothing, except acceptance is hard to comprehend. We do nothing to Deserve Gods grace, it is just a gift, that cannot be earned by works, By grace we are saved thru Faith.
It is not rewarded for good behavior, God just loves us unconditionally.
For a child, I guess, one would just say i do this because i love you, not for anything you have done to deserve that love. ITs just unconditional, i just want whats best for you.