When In Rome

Do as the Romans Do.

From Wikipedia:

St. Ambrose displayed a kind of liturgical flexibility that kept in mind that liturgy was a tool to serve people in worshiping God, and ought not to become a rigid entity that is invariable from place to place. His advice to Augustine of Hippo on this point was to follow local liturgical custom. "When I am at Rome, I fast on a Saturday; when I am at Milan, I do not. Follow the custom of the church where you are." Thus Ambrose refused to be drawn into a false conflict over which particular local church had the "right" liturgical form where there was no substantial problem. His advice has remained in the English language as the saying, "When in Rome, do as the Romans do."

For more information on MJWB's personal encounter with St. Ambrose, click here