You've been through so much trauma in your life that you have developed triggers that cut your emotions off. When this happens you become unpredictable. Your attacks have advantage and attacks made against you have disadvantage. Additionally when you enter this state you must succeed on a DC 16 Wisdom saving throw. On a fail the dm takes control of your character for your turn. You must make the saving throw again at the start of your turn if you failed the previous turn until you succeed. Each failure has the same result.

Triggers

You witness an ally drop to or below half health

You drop to or below half health

Or you can come up with your own triggers.

When you take this Flaw you may take an additional feat.