Yes i know it sounds stupid, however facing fears builds tolorance once they are seen for what they are.
Also since nightmares are more, in my case likely to be remembered than dreams building enough tolorance will likely increase the ability to remember them. Remember dream spells and book writing them down doesnt help. Please let the spell not be to a god/godess as its against my style.
Between black and white the infinite grey
May shall i slip between
Could easily be a spell to increase one's range of reaction, or moral vareability slightly if altered/added to by the person whom casts it. Just an example. Some thing where its focusing before bed instead of words would work too. Style matters a lot, this isnt that weird magic with the k. That spelling is just offensive to my style so any spell involving a god, or ritual would fail and offend it.