and my mouth will declare your praise....
Millions of loyal Christians open their day with this prayer, afixed as it is to the beginning of the Roman Catholic Liturgy of the Hours. One can see how readily this single phrase from the Psalms (51:17) can be adapted for that purpose.
Here are some encouraging words on that very topic from the Journal of a Soul, the diary of Blessed John XXIII:
"When we think that these words are repeated at all Matins, in the name of the Church, who prays for herself and for the whole world, and repeated by innumerable lips opened by the touch of the grace they have invoked, the vision broadens, comes alive and is fulfilled. Here the Church is seen not as a historic monument of the past but as a living institution.
Holy Church is not like a place that is built in a year. It is a vast city which must one day cover the whole universe: “With the joy of the whole earth is Mount Sion founded; in the far north the city of the great king” (Ps 47,3). The building was begun twenty centuries ago, but it spreads and stretches through all lands until the name of Christ is everywhere adored. As the Church increases so new nations, hearing the good news, rejoice: “And when the Gentiles heard this, they were glad” (Acts 13,48). The pious and daring commentator concludes with a thought that is very fine and uplifting for every priest as he reads his Breviary: everyone must take part in this building of Holy Church.
He whose work is preaching this grand enterprise must, as a messenger of His Gospel, say to the Lord: “Lord, thou wilt open my lips and my mouth shall declare thy praise”. A priest who is not engaged in missionary work should long to co-operate in the great task of the apostolate, and when he reads the Psalms privately in his cell he also should say: “Lord, thou wilt open my lips”, because even there, through the communion of love, he must consider as his own voice any voice that is at that moment announcing the Gospel, the supreme praise of God which has given us the theme for this verse more charged with hidden mysteries than with words."