Anselm said "I believe so that I may understand," and "faith seeking understanding." This was an idea borrowed from Augustine who said "believe so that you may understand."
Can we believe a judgment that we do not understand? For instance, could I believe that "bliks are grue" if I don't know what these words mean? And is this what "mysteries of the faith" require of persons? If so, which logical contradiction or absurdity should we believe?
In contrast to this, I argue that we can only believe a judgment to the extent that we understand it. Knowing what a judgment means is a prerequisite to knowing if it is true. In this sense, we cannot believe to understand, nor can faith be seeking understanding. Rather, we have faith to the extent that we understand, and any challenge to a person's faith is a challenge to that person's understanding.
This means that blind faith, sometimes heralded as a virtue, is the acceptance of a judgment without understanding meaning. This should be labeled fideism, and not confused with faith, which can be understood as the evidence of things not seen. In that sense faith is not in contrast to reason, it is in contrast to sight.
A mystery is an unfolding story where greater information is given as the story progresses. A mystery is not a logical contradiction or a judgment empty of meaning. Imagine coming to the end of a mystery novel and finding out that the riddles are solved by the introduction of a square-circle. One would consider the story a waste of time. The "mysteries of the faith" are not paradoxes, where these are self-contradictory judgments. Rather, they are growth in understanding as more revelation is given.
Keeping these distinctions in mind can keep us from confusing fideism with faith, or contrasting reason and faith, or heralding self-referential absurdity and contradiction as virtuous.