Worthiness
Literally asking for a friend.
I know a person who by all external appearances is confident without being arrogant and a greater than average magician. This person deeply believes there is a level of core unworthiness that both reduces his magickal ability and leads him into occasional stupidity, if he is not careful. Is there anything in GoM that may cure this within him? He is familiar with Demons of Magick but not the rest of GoM books.