In Buddhism, where cultivation of peace of mind is the way, there is a slow disciplined journey to greater mindfulness, and for Buddhists, there is the faith that this development will help end suffering. This is a practical path, but sometimes slow going, and often you don't get where you thought were headed. In Zen and Insight meditation (I don't know much about the other schools) we are taught that visions, altered perception and spontaneous joy may happen but are not the goal, and if one is attached to these experiences it can interfere with the practice.
I realize that what I have said so far is a bit of a digression, but I hope you can see the relevance.
Are the insights, visions, and joyful emotions experienced on psychedelics 'real'? When experienced, certainly, but I think many of us have found that what we felt or saw is hard to integrate. And perhaps it was so beyond our frame of knowing that it is almost impossible to integrate, except that we have some sense of an 'other side' or 'over there' where knowledge can not follow.
But are these sort of suddenly transcendent experiences limited to drugs? How often in a moment of resolution have we said 'I am through being resentful; I forgive all people!' and then, two weeks later, we are again bitter with our co-workers, blaming of our family and so on. And yet we were quite sincere in our resolutions! How often will we find ourselves totally enamored of another person, feeling indeed a divine presence in our love for them, and then as quickly as it came it disappears, and all we have left are trivial criticisms: she was superficial, she was flighty. And yet we only two months before loved her with what we thought was the extent of our whole being!
As you can tell, I am heavily influenced by Buddhist thought and am here speaking of the nature of impermanence. Not real, not fake.
Now, I do not mean to say that forgiveness and love are totally relative! I belive with utmost conviction that we should move toward greater forgiveness and love. But at times, as if from a mountain peek, we get a glimpse of our destination and feel as if we have arrived, only to find that the road is still a long travel! What the wisdom traditions teach us is that the love is in the journey not the destination ... even so far that the epiphany is not delusion but itself a part of the enfolfing life.
In some regard, what the Priest said has value: is it useful, is it healthy?
Some people eat mushrooms every so often, do not become attached to their transcendent experience, find a wholeness or a freedom or a new way in their experience, and integrate or perhaps do not integrate the experience and are happy. That is a way.
Also of course people dabble in cocaine at parties, under the influence feel 'connected' to their friends, feel motivated, feel 'real' and become attached to this authenticity so much that real life begins to feel barren and more and more they return to the drug until that is the one and only part of their life with any consistency or passion! This is also a way.
(maybe it is wrong of me to use those particular drugs as an example, but that's my prejudice)
As monkeyjunky noted, the visions and epiphanies of prophets and saints were in many cases precipitated by fasting, and some have speculated that various spiritual teachers may have been epileptic or bi-polar or so on. The life of a prophet or saint is not necessarily the easiest path but for some that is their calling.
So, the Buddhists say beware attachment to the fruits of the experience and I say the same!
take care,
Nic