When trying to accomplish something difficult, like sustained weight loss, it can be helpful to identify a "Primary Goal". A Primary Goal is your main and most motivating reason for losing weight and usually has to do somehow with improved quality of life. It is specific and measurable, so you know when you've achieved it.
Primary Goals can change over time. Some examples are:
I want to be able to walk 2 miles without stopping to rest.
I want to be able to play catch with my child at the park.
I want to reduce the amount of high blood pressure medication I take.
I want to feel self-confident enough to go to the holiday party.
Try writing your Primary Goal on pieces of paper or post-it notes and place them where you'll see them