Thought I'd bring this discussion over here. While it is RAW, I certainly don't ever believe that was the intention of the authors to penalize someone who masters a spell. It is entirely counter-intuitive that someone with Magic Addiction who has put effort into mastering a spell is worse off than someone who hasn't mastered a spell. I stirred the pot over in Spell Mastery and Ritual thread in the main Ars Magica forum, because it is clearly an example of where the authors intended for it to be a stressful situation, but instead said stress die, much like my interpretation of the use of stress die in the Ritual Magic thread. I think it should be stressful situation for Magic Addiction, definitely not stress die.