I just told you. Whatever is on our heart in our own words speaking to the Father in the name of Jesus. Often throughout the day there is praise and a genuine thank you. There is often a request for grace and peace for those hurting or healing with regards to the will of God. That personal relationship transcends using rote recitation of formal “Prayers”.
You cited: Matthew 6:7 - But when ye pray, use not vain repetitions, as the heathen [do]: for they think that they shall be heard for their much speaking. - to describe Catholic prayers of the faithful. This is a classical example of the fallacy in sola scriptura. Jesus' focus in this instruction is on the "vain," and not on the "repetition." It was a condemnation of empty prayers to pagan gods. Two verses later, Jesus gives us the Lord's Prayer. This is a main prayer in Catholic prayer life. It is neither empty nor pagan. It is Holy and honorable and worth repeating because it has meaning.
In Matt. 26:44 - for example, Jesus prayed a third time in the garden of Gethsemane, saying the exact same words again. It is not the repetition that is the issue. It's the vanity. God looks into our heart, not solely at our words. We see in Luke 18:13, that the tax collector kept beating his breast and praying "God be merciful to me, a sinner." This repetitive prayer was pleasing to God because it was offered with a sincere and repentant heart. In 1 Thess. 5:17 - Paul commands us to pray constantly. Good repetition is different than vain repetition.
That personal relationship transcends using rote recitation of formal “Prayers”.
Have you ever read the Book of Psalms? Take a look at Psalm 136. In this Psalm, the phrase "For His steadfast love endures forever" is more repetitious than any Catholic prayer, and it is God's divine Word.
There is much more to a Catholic prayer life than rote prayer. We pray prayers of adoration, prayers of expiation or contrition, prayers of love or charity, prayers of petition or supplication and prayers of thanksgiving. The types or prayer are vocal prayer, meditation, and contemplative prayer.
Peace be with you