Nanc, I struggled with that big time!!! I've been on the path to surgery 3 times in the past decade. The two previous times, I crushed the pre-surgery weight loss and felt confident I could continue on my own. I cancelled my surgeries and did just that.
The first time, I went on to loose close to 90 lbs, the second time, just over 80. But both times, I put the weight back on within a year or two, plus some bonus pounds. So even if you can get up the determination and succeed at first, unfortunately diets alone almost always fail you eventually.
Each time we diet, there are actual physiological changes to our chemistry and hormones that make you gain weight easier and less resistant to weight loss. It's like once we went on our first diet in childhood or teens, we set ourselves up for this downward spiral toward obesity.
This third time, I actually went through with surgery. I'm capable of loosing weight on my own (temporarily), but I need to have a permanent tool in place to finally keep it off! It still takes a lot of determination but I know that in future times of weakness, I can no longer physically eat a whole pie. That brings me a since of reassurance.
I'm not telling you that you can't loose the weight and keep it off without surgery, if you think you can, I'd be very happy for you. It's just that realistically, the percentage of the obese population who can, is minuscule.