Spiritual errors are usually not outright lies but distortions of truth. That way they seem more plausible and can be more effective in taking one off the straight and narrow path. Two such modern errors or heresies, if you can call them that since they are not really Christian heresies even if they have infected Christianity, are almost opposites. One is that the love of one's neighbour is the pre-eminent mark of a spiritual person. This could only be believed in a materialistic world. The pre-eminent spiritual quality is love of God. That should go without saying since Jesus said it. Love of one's neighbour comes after love of God and, properly speaking, is dependent on it which tells us that love of the neighbour means acting for his spiritual good, doing what will bring him closer to God. Love always means working for spiritual good. If you think you love your neighbour but use that supposed love to solidify him in his sins you are not responding to real love at all but to some imagined imitation of it.
This inversion of the true spiritual order has come about, as so many errors do, because one aspect of spiritual teaching has been emphasised at the expense of others which are neglected. The story of the Good Samaritan has been taken as the central pillar of Christianity with more important teachings such as for instance the love of God, the recognition of Christ, the rejection of the world and the fact of good and evil as spiritual realities downgraded. But spiritual understanding is dependent on maintaining the correct balance between truth and love, the vertical connection to God and the horizontal radiation to Man, and note that the horizontal radiation can only be real when the vertical connection is true. Otherwise what you do is not radiate but project and what you project is not spiritual love which wholly depends on the spiritual connection being true since that is its source.
The second error of the two I referred to above is the elevation of abstract spirit as the supreme reality and spiritual goal. This idea can be seen in Buddhism, some forms of Hinduism and even elements of Green philosophy. But it misses the point that God looked at creation and saw that it was good. Why create just to throw the fruits of that away at the end? Creation must clearly add something new and better to the mix and this was demonstrated by Jesus at the Ascension. He didn't just disappear as a spirit. His body was resurrected and then ascended into heaven as Christian teaching says ours will be. Now, this doesn't mean we will all rise from our graves in our old bodies. The body will be transformed but we will still have a body as indeed we must if we have an individual self. Can you imagine a self without a form in which it appears? No body means no beauty. It means no love for love requires appearance if it has any blood in it. Maybe it is creation that gives blood to spirit as in the loving warmth of life.
Abandoning materialism for spiritual belief is a step forward but it can also be a step away if one is not careful. Spiritual error lies waiting for all of us when we set out on the path to God but it is also a good marker of right motivation. We may believe what it suits us to believe. On the other hand, if our heart is true what we believe in our head is of secondary importance.