From experience there are some distinct differences between how the fit think and how the unfit think when it comes to fitness. A few examples, in no particular, order are
– the fit think differently about food
– the fit know when and how to recover from exercise
– the fit know what intense exercise entails
– the fit understand specific measurable goals
– the fit know they will reach their fitness goals not if they will
Basically, their entire psychology (when it comes to fitness) is different between the two groups. This is not to say they are unsuccessful in other areas. In fact many times they are very successful in a lots of areas. On the other hand, when you take the same person and they become more fit their lives are enhanced.