12 The spiritual life, however, is not limited solely to participation in the liturgy. The Christian is indeed called to pray with his brethren, but he must also enter into his chamber to pray to the Father, in secret ; yet more, according to the teaching of the Apostle, he should pray without ceasing . We learn from the same Apostle that we must always bear about in our body the dying of Jesus, so that the life also of Jesus may be made manifest in our bodily frame . This is why we ask the Lord in the sacrifice of the Mass that, "receiving the offering of the spiritual victim," he may fashion us for himself "as an eternal gift" .
Source: Sacrosanctum Concilium (Vatican.va)