[pygy]

"Rational person" is an oxymoron.

A sufficient amount of harassing and violence (both mental and physical) can lead someone to mental breakdown. The threshold may vary from one person to the next, of course, but it can be done.

Furthermore, some studies suggest that depressed people have a more objective assesment of reality (specifically, their estimation of what other people think of them is spot on, whereas non depressed people think that the others see them in a better light than they actually do).

We developed through evolution an optimist bias that keeps most people afloat and allowed humans to survive despite their part of rationality.