Some Evangelicals think the verse, "Do not heap up empty phrases as the Gentiles do" (Mat 6:7 - NRSV) condemns repetitious prayers. But let's look at it. The key words here are "empty" and "Gentiles." The Gentiles prayed to pagan Gods, their prayers were empty, insincere and blasphemous. The verse is a condemnation of empty prayers to pagan gods. We don't think this passage is a condemnation of repetition. The Greek word is "Battologeo", which comes from "Battos," a stammerer. Someone who stutters or uses meaningless syllables. This would apply much more to "speaking in tongues" than repeating a great prayer.
The word "repetition" is not mentioned in most translations of the verse. One could "heap up" empty "free form" praises (that don't repeat) as easily as one could "heap up" a repeating phrase from Scripture. The crucial thing is not whether a phrase repeats, but rather whether it is sincere.
Two verses later Jesus gives us the Lord's Prayer (Mat 6:9). This is a main prayer in Catholic prayer life. It is neither empty or pagan. It is Holy and honorable and worth repeating because it has meaning.
Are not many of the beautiful traditional Protestant hymns repetitious? What about the repetition of "Praise God" during free form worship in Assemblies? Even the angels are eternally in the presence of God repeating "Holy, Holy, Holy (Rev 4:8). This is not empty nor pagan is it? It pleases God. When I do the Rosary, I'm sincere. I'm saying very meaningful prayers that come from Scripture. This makes Jesus immensely happy and He has given me the experience of his love consistently during the Rosary to prove it.