Lex Orandi, Lex Credendi, Lex Vivendi, Lex Agendi (Lex Orandi Online)
All the Truths of the Faith are found in every liturgical act. For in the Liturgy, the Holy Sacrifice of Christ is lived again in an unbloody manner; the Love of the Most Holy Trinity is seen and expressed. The Faith is lived and learned. We are invited into that immense mystery of the Trinity, that Triune Love, which our hearts long for and seek.
Indeed, the way in which we pray reflects that which we believe. This is undeniable and imperative. Yet, we find two things that neglect this vital truth in the importance of Holy Mass: The first is failure to understand and live Lex orandi, Lex Credendi. The second is found in the erred teaching, misinterpretation, and misuse of the Holy Mass.
Thus, the important principle of Lex orandi, Lex credendi – which can be expanded: “Lex orandi, Lex credendi, Lex vivendi, Lex agendi” – demands of the Catholic his acknowledgment, understanding, and obedience. This principle of the early Church literally means that the law of prayer is the law of belief, which is the law of life and the law of doing. In others words, the way in which we pray expresses that which we believe. It is not content of belief that forms the prayer, but rather the substance of prayer that gives the law of belief.
In saying this, then, if the way we pray is changed, then ultimately, what we believe is also changed. We witness this by examining the lives of Catholics today in toto. Where the Protestant is left wanting for the Eucharist, the Catholic is left wanting a catechetical appreciation of his Faith. A Gallop Poll in May 2012, stated that 82% of Catholics say that contraception is morally acceptable.  Another Gallop Poll showed that 68% of Catholic believed that divorce was also morally acceptable.  Both of these issues are against the teachings of the Church.
The enemies of the Church understand this most of all, and have pursued it for many centuries. Beginning with his defiance and culminating with his disobedience, Martin Luther understood that by incremental deviations in the offering of the Holy Mass, the beliefs of the laity could eventually, if not inevitably, be reorganized.
Protestants, by their heretical and defiant practice, have it switched, Lex credendi, Lex orandi – belief over prayer! We can see this when they claim to follow the words of Christ in the Bible, but fail to put that belief in practice.
Hence, by this principle, we can see that logically the error falls in the way they are praying. This is because the way they pray reflects what they believe. A prime example is the truth of the Blessed Eucharist, if they believed Christ's words regarding the Holy Eucharist then they would be offering the Holy Sacrifice of the Mass as Christ did as the perfect worship to offer God. Instead they have a rock concert or hymn singing, or preaching as the focal point and climax of worship on Sunday.
Now back to Catholicism, there has been a decline in worship and at such a huge scale in such a short time. Yet, what a better way to get people to change their belief than to first change the way in which they pray. This might help explain why beliefs had changed as quickly as they did within the Catholic Church because of all the changes in worship and in all 7 Sacraments with Vatican II.
What is more disheartening is how so many ignore this liturgical thorn and choose not to seek or explore the root of its deviation. As we have acknowledged already, where some claim Vatican II has been a wonderful council, many more of the Council Fathers inclined to disagree: “A fructibus cognoscetis eos.” (3)
Again today, it is a very sad fact that most Catholics no longer believe in the Real Presence of Christ in the Eucharist and Mass attendance is at an all time low. (4)
Unfortunately, even those that do go to Mass, because the way of prayer has changed, are poorly catechized in Catholic Truth, and do not know what the Holy Mass really is and does. Another study poll in 2017 showed that 54% "No longer feel that being a committed Catholic requires going to Mass every week"(5)
On the other hand we can see now that there is hope though traditional Catholic parishes which continue to grow even as US Catholicism declines. (6)
Tradition, repetition, and continuity, are what gives foundation, stability, and a constant reminder of the Truths of the Holy Faith. It is precisely in the Mass of all times, the Traditional Mass, where we find all of this. To enter into something in depth requires time and repeated considerations of a thing. Repetitio mater discendi, as we say in Latin: repetition is the mother of learning. This principle thusly plays back into what was already mentioned about Lex Orandi, Lex Credendi, Lex vivendi, lex agendi, and now lex discendi. When things are repeated we become more familiar with it and we are then able to enter more and more into it. Just as a pianist who becomes more and more accustomed to playing, can play more perfectly and enter more deeply into the music, the more it is repeated and continued. Or as a ladder that has repeated planks of wood, yet by each plank, though it is the same, is one able to climb higher and higher.
This principle is most seen in the Traditional Tridentine Mass. Yet, it is not just an empty repetition, but a mysterious living presence, which we enter upon more and more deeply and perfectly each time we offer Mass according to the Will of God and our own dispositions.
This is not present in the new form of the Mass (Novus Ordo) as new things are constantly popping up, repetition is not as constant, and other things like silence which goes hand in hand with repetition in order to lift the mind up into contemplation, is missing. It is often seen that active participation is equated with physical activity rather than the higher and more active form of participation which is spiritual participation, which St. Pius X himself expressed and taught. Therefore, we must not forget Plato’s dictum: “Any change whatever except from evil is the most dangerous of all things.” (7) Traditional terminology and Traditions were abandoned and this new language and spirit of Vatican II which was very ambiguous, and unclear, left a lot to be opened to various and serious erroneous interpretations that have destroyed the majority of Masses today.
In summary, because the way Catholics today pray was changed, then ultimately, what the majority of Catholics believe was also changed. We need to recognize this so as to be able to know that it is critical to return to that which had always been and always worked, that which was given to the Apostles and had formed the saints from the beginning. The Holy Sacrifice of the Mass in all its beauty, truth and goodness, in the Traditional Tridentine Latin Mass.
 Gallop Poll, (Princeton, NJ, May 2012) last accessed http://www.gallup.com/poll/154799/americans-including-catholics-say-birth-control-morally.aspx on 11/16/13.
 Gallop Poll, Moral Acceptability of Six Issues Based on Gallup Polls Conducted in May 2002, May 2003, and May 2004 (Princeton, NJ,) last accessed http://www.gallup.com/poll/15550/US-Catholics-Vary-Widely-Moral-Issues.aspx on 11/16/13.
(4) (https://news.gallup.com/poll/232226/church-attendance-among-catholics-resumes-downward-slide.aspx and https://onepeterfive.com/only-26-of-us-catholics-under-40-believe-in-the-real-presence-and-thats-no-accident/ and https://www.pewresearch.org/fact-tank/2019/08/05/transubstantiation-eucharist-u-s-catholics/)
"Traditional Catholic parishes grow even as US Catholicism declines": https://www.washingtonexaminer.com/news/traditional-catholic-parishes-grow-even-as-us-catholicism-declines
(7) Laws, No. 797.