I have always disliked the saying, "Perception is reality." If taken literally, this saying indicates that one's perception is equal to objective reality. While that is a false claim, too many people believe it. "That's your truth, not my truth" kind of stuff. What people should mean by the saying, "Perception is reality," and what I would agree with, is "One's perception can have a real impact." Hitler's perception of Jewish people was clearly not in accord with objective reality, but his perception had a devastating impact on the European Jewish community.
St. John Chrysostom in his Homilies on the Gospel of Matthew, 370 A.D. (Homily 82, section 4), talks about the Eucharist in a way that reminds us that perception is often not reality:
Let us therefore in all respects put our faith in God and contradict Him in nothing, even if what is said seems to be contrary to our reasonings and to what we see. Let His word be of superior authority to reason and sight. This too be our practice in respect to the Mysteries [i.e., the Eucharist], not looking only upon what is laid out before us, but taking heed also of His words. For His word cannot deceive; but our senses are easily cheated. His word has never failed; our senses err most of the time.
When the word says, "This is My Body," be convinced of it and believe it, and look at it with the eyes of the mind. For Christ did not give us something tangible, but even in His tangible things all is intellectual. So too with Baptism: the gift is bestowed through what is a tangible thing, water; but what is accomplished is intellectually perceived: the rebirth and the renewal. If you were incorporeal He would have given you those incorporeal gifts naked; but since the soul is intertwined with the body, He hands over to you in tangible things that which is perceived intellectually. How many now say, "I wish I could see His shape, His appearance, His garments, His sandals." Only look! You see Him! You touch Him! You eat Him! (The Faith of the Early Fathers by William A. Jurgens, Vol. 2, p. 112)
So let us remember that reality is reality, whether we accept it or not, whether we perceive it or not. And let us also remember that saying that the unreal is true has very real, very detrimental effects.