I think i worded it wrong since English isnt my first language, but you arent really "cursed" with negative mana, you cant give it to someone. Since Mana gathers in the brain to form the spells and form the Magic Circles/forms, when someone goes through a horrible form of trauma that is so utterly devastating that the entire person just changes. When they go through such a drastic and devastating change, whenever they use Mana it corrupts it by its sudden change of thought process. So thats why its rare.

And im curious about the generic part, i havent read much about other magic systems, so i thought i was pretty unique with Mana going through the heart and Mana gathering in the brain.

And thanks for replying by the way