Mixing our own inventions in the ordinances of Jesus Christ

"Keep to the institution in the sacrament. Though you may think it a more mean way, yet you will find a greater beauty in this ordinance than you ever found in all your lives; for the more we keep to Christ's institution and mingle nothing of our own, the more glory and beauty and excellency appears in the ordinances of Jesus Christ. But when any man shall mix any if his own inventions, though he may do it to a good end and think to add to and put a greater luster upon the sacrament, the truth is that what he thinks to be a greater luster, reverence, or honor upon it rather takes off the luster and glory of the sacrament. Then are the institutions of Christ glorious when there is no mixture among them." GW pp. 261-262