Items that have Drain Personality and where you'll find them:
Helm of Ferocity ( Drain 5 pts ) - Skingrad, Hammer and Tongs
Scales of Pitiless Justice ( Lowers Personality 2 pts when in inventory ) - Quest reward for the
Scheduled for Execution, Dark Brotherhood quest.
Diseases that have the Drain Personality effect and where you're likely to catch the disease from:
Brown Rot ( 5 pts ) - Zombie
Greenspore ( 10 pts ) - Zombie, Slaughterfish
Rust Chance ( 5 pts) - Zombie
Serpiginous Dementia ( 10 pts ) - Headless Zombie
Of course, if all that fails you can temporarily alter your personality with the console provided that you are on the PC.
Player.ModPCA Personality #
# being a negative number based on how much you need to lower the attribute.