If you are at Rome live in the Roman style; if you are elsewhere live as they live elsewhere. [Lat., Si fueris Romae, Romano vivito more; Si fueris alibi, vivito sicut ibi.]
When I am at Rome I fast as the Romans do; when I am at Milan I do not fast. So likewise you, whatever church you come to, observe the custom of the place, if you would neither give offence to others, nor take offence from them.
When I am at Rome, I fast on a Saturday: when I am at Milan I do not. Do the same. Follow the custom of the church where you are.