This is a great question. Because of our own individual circumstances, there are ultimately many possible reasons that a person may want to stop exercising. However in my own experience I’ve seen 2 common things that will discourage someone and cause them to consider stopping their exercise.
First, I see many people who are putting forth the time and effort to exercise but not seeing results. They feel as though they are holding up their end of the “exercise bargain” (and they are) but their bodys are not, and frustration sets in because they don’t see something for all the work they are doing. As I begin to work with them we typically discover the problem has been that the exercises were being performed incorrectly, or the level of the workout (intensity) was a bit low, or a combination of the two. The good news is that the fix is easy in these cases. Since the desire to exercise is already there it’s just a matter of teaching them how to do it correctly. They then begin to see something for their work. It’s exciting, and instead of wanting to stop they’re driven to continue.
Second, I see some individuals who come to a point in their lives where they want to see major changes very quickly. They begin exercising all the time, as hard and as often as they can. This kind of exercise regimen is next to impossible to maintain. Their bodies wear down or they become injured, and exercise stops altogether. This also leads to frustration because they feel they are unable to keep up with this false perception of what exercise is. As I begin to work with them, we take it back a bit and redefine things. Most importantly I encourage them to see exercise as part of a lifestyle, and not something you do for a short time and then stop. Defined this way, we are able to develop a realistic workout schedule which provides the exercise they need as well as the rest and recovery that they also need. Most are surprised (and relieved) to find that they can have both exercise as well as a life.