I like the ideas everyone’s put forth so far, or extensions of them like a daily (periodic) amount of investiture, and it’s cool to see where other people’s minds go!
My first thought was: magic that gets less powerful the more emotional you are, or the less in control you are. Kind of like how Awakening is linked to perception and cognition and better awakeners are better at imagining what they want their Awakened objects to do and giving commands, better casters in this system would be better at keeping their emotions in check. You could then end up with caster battles that were super inflammatory and all about the caster’s ability to keep their cool under pressure, almost like a rap battle where emotional control is paramount. It’d be cool too to have a magic that was that reliant on perception and the cognitive realm in a new way. I realized as I was writing this that it leans pretty hard on the first definition and might better fit like a shard of Discipline or something but I still think it’s cool and could be a cool idea for a system!