The assumption seemed to be that human beings normally feel good, or at least fine, and only an affliction of some kind, either short- or long-term, could explain why someone would feel bad.
Productivity is a tricky thing. The more we do, the more we should feel accomplished. A sense of doing should bring about a sense of peace--or so I thought.
Are there certain beliefs or reasons that are behind the bad habits? Is there something deeper — a fear, an event, or a limiting belief — that is causing you to hold on to something that is bad for you?
That said, the study cited above found the average habit takes about 66 days to become automatic. (Don't put too much stock in that number. The range in the study was very wide and the only reasonable conclusion you should make is that it will take months for new habits to become sticky.)