Some of the things that help me stay motivated:
Remembering that this isn't a "diet" - it's a lifestyle change! It's not about depriving myself, but rather learning healthy habits. And because it's a lifestyle change, I also have to remind myself that this is a marathon, not a sprint. I didn't put this weight on overnight or develop my bad habits overnight, so change won't come overnight either. Those are the things I use to get over bad days and setbacks.
I like to have motivational words around me as much as possible. I've been known to lipstick short quotes on my vanity mirror, put up motivational signs on the fridge, tape reminders to workout instead of loafing on the TV and computer screens, etc. I try to keep all of the messages positive and uplifting, rather than chiding or negative. [For all you Harry Potter book fans out there, when I think of chiding reminders, I'm always reminded of the homework planners that Hermione got for Ron and Harry: "Don't leave it 'til later, you big second rater!" LOL]
I've also found that staying active on SP and these forums really helps me to stay motivated. As I'm giving advice to others, it reminds me of the same information. And reading other people's ideas gives me new ideas and directions that continue to motivate me.
Good luck on your journey! Glad you're back!! :)