"Many believers want nothing more than to witness a miracle to justify their faith in God. But there are others who have lost their faith after seeing too many miracles."-- line spoken by main character Ivan Isaacs in the 1998 Korean manhwa PRIEST, Volume 4, Min-Woo Hyung.
The above utterance has a very specific meaning in this Korean "horror-western," whose protagonist is a priest who has accepted the help of a demon in order to battle another demon. As I've not finished the PRIEST series, I can't say how assiduously this idea of "too many miracles" is pursued throughout the narrative. I can only say that in Volume 4, the idea is not pursued in depth.
What interests me, though, is the dynamic suggested by the phrase "too many miracles." With the exception of "intellectual religions" not rooted in everyday life, such as Deism, most religions depend on some sort of miracle that supplies the evidence of things not seen, be it a specific entity (gods, demons, et al) or a general principle (Buddhist enlightenment).
Mircea Eliade illuminated this dynamic in his book PATTERNS OF COMPARATIVE RELIGION, where he asserts that every hierophany (manifestation of something sacred) is inevitably also a "kratophany," a manifestation of power. The latter manifestation can be something that demonstrates a holy figure's ability to step outside the normative laws of mortal life, as in John 20:24-29 of the King James Bible, which details the appearance of Christ before "doubting Thomas." However, even religions that do not depend on the question of "faith" as greatly as does Christianity require miracles to demonstrate that the religion is more than mere opinion. In some versions of the illumination of Buddha, his contemplation beneath the Bodhi-tree becomes a matter of cosmic consequence in that legions of demons attempt-- and fail-- to distract him.
However, "too many miracles" could become as onerous as "too few." Thus in PATTERNS Eliade observes that kratophanies "emphasize the extent to which the manifestation of the sacred intrudes on the order of things." To pursue the idea eludicated by the manhwa-author, one might speculate that if one did exist in a world of "too many miracles," that the "faith" one might lose would not so much be faith in "higher powers," but rather faith in "the natural order of things," which might come to seem nothing but a meaningless illusion. That many religions have advanced this conceit, often to compete with the common-sense view of the order of things, is no coincidence, and the idea points to the ambivalence Eliade senses in the sacred, since it threatens to undo the comfortable aspects of the profane world in which mere mortals dwell.