I think it's easy to fall into this automatic thought process of well I've never been successful at that so it's out of reach for me. Well here's some self excavation that can help quash those thoughts:
How long have you been trying to get this right for? A year, two years, your whole life? We all have only so much energy to expend each and every day on different things that make up our existence, and as a result things get triaged, prioritized ...
So what priorities became more important in your life at those times when you were just not able to get this right? Job, family, move, break up, tragedy, pregnancy? If you analyze it you will see you were focused on, and manifesting or healing from, things in life other than a healthy weight and as that took priority, the weight loss fell by the way side. In the end it has nothing to do with success or lack thereof, it has to do with whatever you allow to be the driving factor in your life at any given point in time.
My husband is a great example of this. He has been on a swim team since the age of 5. Well he is 46 now, going on 47. In the early years of our marriage I would throw a fit sometimes over his dedication, of course I expected him to spend every free second with us. As maturity set in I learned to let it go and admire him now for his dedication and commitment to his health and body. It has often times meant he's had the boundless energy to manage things I just haven't been up for. But at the same time it is also a reminder of how when you expect continued results it needs to be a lifelong commitment.
What will you prioritize today that you can take into your future?