Yes, and you always will be at "cross purposes," for the very good reason that there is no authority other than human for the observance of the day, and there is not even human authority for what you call "a due observance." When the human will be the only authority, it is only natural that there should be "a diversity of usage"; it is only natural that many should allow themselves to do what others will not allow themselves to do. There is, however, a most excellent remedy for all this. That is the commandment of God. God said "The seventh day is the Sabbath of the Lord thy God; in it thou shalt not do any work." "A due observance" of that commandment will give you the advantage which you so much need in urging upon others the obligation of the Sabbath. But as for keeping Sunday, you will always much need the advantage in urging its obligation upon others, until you grasp the arm of civil power and do by it what there is no authority of God for doing at all.