Three Distinct Sources
of Private Revelation
OK, let's have a look at what the Church says about private revelation. It can come from only three possible sources: Satan, God, or self-delusion. There are distinct characteristics that come along with each category. Let's examine them.
For diabolical manifestations, the people involved (both the mystic and the recipients of the messages) cannot truly become holier, be drawn to the sacraments, or exhibit authentic humility. Further, they will manifest any of the following: anxiety, piqued curiosity, interest in material gain, attachment to the things of this world, pride (typically in knowing something others don't), and/or a tendency toward division and accusation.
For heavenly communication, the persons involved must necessarily be drawn to humility, love, and personal sanctity. Spiritual directors are the best people to determine personal response to said manifestations. An outside (much less casual) observer would be hard-pressed to accurately diagnose interior dispositions from distant reports. Also, supernatural physical signs that point toward heaven (bleeding Eucharists, stigmata, sacramentals changing to gold, etc.) are wonderful indicators that something from God is transpiring. At least, they elude scientific explanation--pointing to the spiritual realm.
Determining that an event is self-induced is a little more difficult, assuming that there are no supernatural occurrences. Close personal observation is necessary to determine the subject's state of mind, relationship with others, and standing with the Church. These give a professional reviewer invaluable information.
Now, we have a small understanding of the three DISTINCT categories that these manifestations can find their source in. A case cannot fall into two of the above categories. Fully comprehending this point is invaluable. When one of the three sources is ruled out, you only have two more choices left. If there is something supernatural going on, it cannot be self-delusion. If the event has ecclesiastical approval, then it cannot be from hell. If the purported messages deny some tenet of the faith, then it cannot be from heaven. The rules are quite simple.
The salient point is that deciding whether someone is an authentic mystic is not a light task. It is not one to be whimsically (or worse--emotively) reached. Just because one 'thinks' that someone is not an authentic visionary because the messages don't mesh with his own idea of what God should tell us, he cannot simply proclaim the case invalid. This is both unfair and potentially dangerous to his soul.
Let us not forget that God works in mysterious ways. His ways are as high above ours as are the heavens above the earth. If we confine Him to the tiny little box we might impose on ourselves, then we are in for a rude awakening.