Oh, I had forgotten that bit (just reread the first few chapters). For some reason I thought it was part of the curse as the god had casted it while "asking" him to forget about his feeling of resentment toward him, and that it was supposed to be mental as well. Damnit.
I mean, I remember the lab stuff, but I don't remember the author showing anywhere, in the manga, that experience being relevant to how he overcame that curse.