Everything Hits At Once

I wonder if a descent into madness is really a slow process or a rapid decline. Do people have any idea what's coming. When someone like Hitler or Syd Barrett or Donald Rumsfield lost their mind, do you think they experienced a couple of moments when they said to themselves "You know, I'm pretty fucked up...maybe I should be concerned about this?" And then they just chose to ignore those signs and keep on keepin' on until it was way too late?