From what I've read on prelest, as a layman who has investigated this concept carefully, it sounds very possible that you fell into it. The mechanics of how the First Friday devotion would cause it are beyond me, but the numerous apparitions received by individual Catholic monks in isolation and the frequency and relative ease with which these are accepted is unparalleled in Orthodoxy. I am of the firm opinion, though I a, a layman and the decision is up to the bishops, that the one thing that must go as part of Roman Catholic - Orthodox reconciliation is the vast majority of personal revelations, in particular all of those which consist of either Jesus or Mary promising some very specific spiritual reward to someone who completes a specific and complex devotional task. Frankly it sounds as though the demons just enjoy making Catholics do such things for their own sick amusement.
There is also to be considered the fact that many Orthodox, and even an 18th century Pope, regarded devotion to a body part of our Lord as absurd and indeed as Nestorian.
Now some Orthodox like to downplay prelest, for example, the late Metropolitan Anthony Bloom, but I would note Metropolitan Kallistos Ware does not shy away with it, and the Philokalia (which Bloom argued should not be read by laity) abounds in it. I think that prelest, as the idea that we should be watchful against spiritual and mental traps for our mind from the devil, is among the most important teachings specific to Orthodox Christianity. Mid you look at Roman Catholics and Pentecostals, they lack discernment, whereas on the other hand other Protestants tend to show an excessive rationalism and disbelief in the supernatural that itself runs contrary to the apostolic faith and is a relic of the Enlightenment. Prelest as a concept is what enables us in humility to evaluate the supernatural with extrme caution and avoid getting into trouble.
The message of the Philokalia to me seems to me that a monk who sincerely repents can see the uncreated light of God, but those who pursue visions or supernatural experiences or lack humility will fall into prelest and be destroyed. This message seems to repeat itself throughout the book. But it is especially clear in St. Symeon the New Theologian's discourse on the Three Methods of Prayer. One can also see it as a major theme in the sayings of the Desert Fathers.
I don't understand why Metropolitan Bloom and others like him were and are against sharing the Philokalia and the doctrine of prelest with parishioners, since it is such a useful means of spiritual self defence. Perhaps in the rarified English society Bloom feared his flock might flee the church, thinking it was superstitious, if these subjects were discussed. However, both my confessor and I are of the opinion that prelest and the avoidance thereof is an essential Orthodox teaching that one can trace back to the teaching of our Lord on wolves in sheeps clothing, and the Epistles. Parts of the writings of Paul, Peter and John seem to be almost entirely about avoiding spiritual deception, which in the early days of the church usually consisted of falling into the early Gnostic cults such as that of Simon Magus and his disciples, or Docetism, or the Judaizing sects. But prelest has been there from the start.