> If someone asks you, in a very convincing, persuasive way, why you did something a year ago and you can't clearly remember you did, it can happen that you become positive that you did so anyway. And then the mind just hallucinates a reason. That's a trait of brains.

Yes brains can hallucinate reasons, doesn't mean they always do. If all reasons given were hallucinations then introspection would be impossible, but clearly introspection do help people.