Hello Pamela, I have thought about this since the day you asked the question. I think every one's motivation is unique to them. For me, it was being unhappy with the way I looked. Not as simple as that really though. When I was younger, I was defined as tall and skinny. I had pride in that description. So, when I wasn't skinny anymore, I needed a new definition. I found it in motherhood. Now that the kids are grown, I found I needed another description. I found that too. The best motivation for me was for me to always try to be my best. Being sort of a control freak, I couldn't let a thing like added weight have any control over me. Let's face it, how you look affects how you feel. I don't want to feel overweight. I want to feel good and to look good, for myself and for my husband. I still have work to do because I do not like the little mommy tummy that I still have after all of these years.
If and when it becomes important enough for you to do, the motivation to do it will be there, assuming that there isn't a health or other issue involved. Our lives are ordered by priorities, when losing weight becomes a top priority, you'll get it done.
I wish I had a better answer for you, a formula that was sure to work. But that is why there are so many special diet plans out there, because they all don't work on everyone. Everyone is unique and we all have our own bridges to cross.