Example Scenario: PersonA wants to do something, but is told they can't. They're persistent, and they quiet down eventually, but then they find just the slightest justification and jump back into hours-long pleading again as if the past conversations never happened.
I could say that PersonA is a wishful thinker, but "wishful thinking" doesn't necessarily have a negative connotation. PersonA in this case is a wishful thinker to the point of lunacy. Is there a single word or phrase that accurately describes this so that even when heard out-of-context it would be understandable? Optimally it'd be workplace-appropriate, but it's fine if it's not.