Why do some people manage to stick to a workout regime....... and other's fail miserably?

So I was thinking this morning, what is different about the people that stick to an exercise program - or what is different about that person at that exact time in their lives? Why do some people get better results, and why do other's end up feeling like they are wasting their time.

Here's what came to mind....... 1. CONSISTENCY - they set themselves a schedule and come hell or high water they stick to it. Almost nothing will get in the way of their exercise.... They fully realise how important it is for themselves and their familes to stay healthy and so they do it. End of. Some people like having a timetable and are not easily swayed from it. This helps massively with keeping on target with any type of exercise plan.