6 You ask me whether you ought to fast on the Sabbath and to receive the eucharist daily according to the custom— as currently reported— of the churches of Rome and Spain. Both these points have been treated by the eloquent Hippolytus, and several writers have collected passages from different authors bearing upon them. The best advice that I can give you is this. Church-traditions— especially when they do not run counter to the faith— are to be observed in the form in which previous generations have handed them down; and the use of one church is not to be annulled because it is contrary to that of another. As regards fasting, I wish that we could practise it without intermission as— according to the Acts of the Apostles — Paul did and the believers with him even in the season of Pentecost and on the Lord's Day.
They are not to be accused of Manichæism, for carnal food ought not to be preferred before spiritual. As regards the holy eucharist you may receive it at all times without qualm of conscience or disapproval from me. You may listen to the psalmist's words:— “O taste and see that the Lord is good;” you may sing as he does:— “my heart pours forth a good word.” But do not mistake my meaning. You are not to fast on feast-days, neither are you to abstain on the week days in Pentecost. In such matters each province may follow its own inclinations, and the traditions which have been handed down should be regarded as apostolic laws.
Source: Letters (New Advent)