The Mormons say they are assured that they are right because of "the burning in their breast."
Experience and alleged supernatural revelation is not a very strong argument. Every mystically-inclined religious person - whether Protestant, Catholic, Mormon, or even Islamic - can make an existential argument. Such an argument is therefore highly dubious, if not worthless.
True, which is why the Catholic Church is very skeptical about such matters, and even if deemed worthy of belief, does not make it a part of the Deposit of Faith. In other words, what happened at Fatima, though worthy of belief, is not a required belief by a practicing Catholic. Private revelations are always subject to misinterpretation.
Regards