Maybe you don't like your job maybe you didn't get enough sleep well nobody likes their job nobody got enough sleep. Maybe you just had the worst day of your life but you know there's no escape there's no excuse so just suck up and be nice.
It's not only imagination it's the distortion of the vision. You suddenly think This person is idealistic this person is strong this person has dreams when you know better most of the time. You put what you want to see on people.