Yes doubting is a hallmark trait of many who lack insight in to themselves and there behaviour,but most people either are gifted with insight at birth or spend lots of time in therapy exploring their inner selves , how do you get into potential diagnosis of MI so it's a vicious circle .
There are people on this forum and peeps I am friends with IRL who have NO down to a point where they know there feelings and moods so well , there doctors give them a variety of medications to have on hand so that if thry feel a problem starting they can shut it down without the "men in white coats"( and no this not men without hats follow up album) hauling them away .

So there are extremes of people that can't see the problem and others who can see it coming and shut down , somewhere in the middle is the grey area of the grey matter ( Sorry I am in joking mood today) that most find themselves in .