Each of us has a different set time when we will give up on doing something. For some of us it is 10 days, others 3 months and still others only a few days. I know that my motivation level is about 10 days to 3 weeks. If I don't see much of a difference in what I am doing I usually give up. That applies to weight loss or exercise for toning.
I have found a wonderful article on motivation for losing weight. You should read it. It is called "Motivation is the key to successful weight loss"