From The Ascent of Mount Carmel; Book Two Chapter 11 by St. John of the Cross

6. The reason is that if the corporeal vision or feeling in the senses has a divine origin it produces its effect in the spirit at the very moment of its perception, without allowing any deliberation about wanting or not wanting it. This is likewise so with the more interior communications. Since God grants these favors without the individual’s own ability and effort, he causes the desired effect of these favors without this ability and effort since he produce the effect passively in the spirit. The good effect accordingly, does not depend on one’s wanting or not wanting the communication.
So, I’m thinking, here’s the danger in becoming attached to and pursuing more of any visions or feelings.... An efficacious fluoride treatment provided by one’s dentist tastes pepperminty. The good effect of the treatment has nothing to do with the peppermint taste. The salutary effect is there, yet is not noticeable to the senses. So it would be foolish to be in search of peppermint. That minty fresh taste may come along at times, but that does not mean it is linked to dental benefits - it could in fact be linked with that which could be detrimental. Candy canes, Altoids, and schnapps may all taste just like the treatment your dentist gives you, but they are not what the doctor ordered.