It is not lack of ambition or motivation

I have been working on improving myself for many years, and in the last year and a half I have been trying to loose weight. I am very ambitious and motivated. When I have a job, I try to give it 200%. I am talented in certain areas, just like most people have a couple of things they are really good at. So why don't I move forward? And what can I do to move beyond what I have achieved so far.
I am not looking for motivation, I already have that. I do not want the key to accomplishing my goals, I've read plenty of books on that too. What I want to analyze in the coming weeks is why, with all the skills and knowledge, some people cannot seem to move past a certain point. I don't want the key to being Oprah or Bill Gates. We've all seen their success stories. I am the kind of person that believes that a person's past does not equate their future. I believe that a person needs more than just wanting something to achieve it. I know that hard work will result in great rewards. Most importantly, I believe that wealth is not just a number of dollar bills in a bank account. Wealth encompasses what you have achieved in your life, the people that surround you and of course, the toys you have too.
I do not want to study the rich and famous to see what am I doing wrong. I also do not believe that depression has anything to do with it, although there are times that I feel sad and it is hard to get out of bed in the morning. What I want to study really carefully is why with all the skills, knowledge, guts and desire, I am not making it happen. And maybe during the process, someone might take my example and analyze themselves, without spending thousands in a doctor's office. (However, if you suffer from severe depression or other psychological or medical problems, you should still see a doctor. I am talking about the average person who just feels a little challenged by LIFE). Keep in touch.