It is always good to base your prayer on prayers coming from the mouth of the Lord.
In this matter those who warn us are right, for if our nature were not so weak and our devotion so lukewarm there wouldn’t be any need to compose other prayers, nor would there be need for other books. As I say, I am speaking to souls that cannot recollect their minds in the thought of other mysteries because they think some kind of skill is needed, and there are some minds so ingenious that they’re never satisfied with any of their thoughts.
So it seems to me now that I should proceed by setting down some points here about the beginning, the means, and the end of prayer. I shall not take time to dwell on more sublime things. No one will be able to take from you these books (the Our Father and the Hail Mary), and if you are eager to learn you won’t need anything else provided you are humble.
Saint Teresa of Avila
The Way of Perfection, ch. 21, no. 3
Teresa of Avila, St. 1985, The Collected Works of St. Teresa of Avila, translated from the Spanish by Kavanaugh, K; Rodriguez, O, ICS Publications, Washington DC.