For me Lithium didn't dull my mind. Instead it calmed my emotional state when in bad episodes. For example when in really bad mixed episodes I don't punch walls, drive like a manic while screaming or impulsively self harm now I am on Lithium. The horror feelings are still there but I am more in control. This has saved my life on several occasions. While stable I still feel a normal range of emotions and can think well. I guess it is different for everyone.