The liturgy does not belong to me, to you, to any priest-celebrant or to any individual Catholic.
The liturgy is given to us by the Church as a means of participating in the worship of God as a family of believers who have come together to worship in unity with the Church.
For this reason, any personal or idiosyncratic alteration of the liturgy by anyone involved is an insult to the unity called for and required of us by Christ when he said, "that all of them may be one, Father, just as you are in me and I am in you."
- John 17:21.
In our personal prayer outside of the liturgy we are allowed much greater leeway to pursue piety as our hearts direct us.
But during mass we are called to unity in Christ.