Those are very mixed and unclear standards then. How can they be reliable?
Moreover, when people self-report, they possibly present a more favorable image of themselves than they actually have most of their time. Someone could be miserable much of their days, but when questioned directly about their happiness, will say that they're quite happy.
For example, when I was little, I was raised to always answer "Thank you, I'm fine" whenever anyone asks me "How do you do?" It was a lesson that I was slow to learn, as I would answer truthfully each time, half of which was that I wasn't fine. After that, I was taught quite explicitly that regardless of how I feel, I must always reply "Thank you, I'm fine". I remember distinctly how exasperated my educators were with me.
I'm quite sure I'm not the only one who raised to always present an optimistic, positive persona.