First of all, BoopRN, let me just say, you are not a failure! You are on here working on getting your motivation back and that is the first step.
Hopefully you're not beating yourself up too harshly for having some troubles getting back on the wagon, because sometimes that can have a bad affect on motivation you know?
As for what motivates me:
1. Looking at the before and after pics of people who have lost weight. I always love a success story.
2. Thinking about how *fabulous* I'll look after I lose some weight. (I usually try to give myself a confidence boost by saying something like, I'm gonna be gorgeous when I'm thin, 'cause I'm already beautiful)(by the way I just do this as a joke, I'm not the best looking chica out there, but I've heard positive thought processes help more than negative beat-yourself-up stuff, so I'm giving it a try.)
3. I plan, I make sure I have a game plan of exercise and I sort of know what I'm going to be eating in a day.
4. I record. I write down my exercise and my food intake in a journal. Even on the days I eat not-so-great foods. I also try to pay attention - on days when I don't eat so well I feel like crap, where as on days when I'm eating whole foods I feel great.
5. I'm getting into dietician work, and I tell myself I have to look the part if I'm going to be giving people nutrition advice one day.
So come on, you are worth it. Take it one day at a time.

You can do it!