This very subject really caught me off guard the other night.
My friend just asked me if I believed I was assured of my salvation. I responded, "of course!"
His response, "Well then you don't need me... or any church... or ANYBODY THEN! Why do you even bother going to church?" He demanded to know. I told him that he was right. I loved him, but that I would not be looking to him for salvation.
I've read that in JW theology, there's no salvation guarantee but to hear the notion fall from the lips of a person you care about is hard. He's working himself silly to gain approval. Correct me if I'm wrong, but it appears that this notion is a key motivator to this acceptance of slavery.