Everyone has their little mental aids to help them keep motivated.
I always struggle with keeping on a diet if I miss a day or two of exercise. It's like something inside says, well, you screwed that up, so to heck with the rest of it. Then I eat like a pig for a couple of days and through the weekend, and promise that I will "pick it back up" come Monday. But often I don't. And even if I do, I've eaten like a pig for 3-4 days with no exercise!!
This site has helped me get off that track for two reasons:
1) The baseline caloric burn graphics demonstrate that the chief catalyst of weight loss is not exercise - it's sustainable calorie restriction. Not to say that exercise isn't important; it builds muscle and heightens baseline calorie burn, etc. etc. But to make me get off the treadmill of viewing a day without exercise as a "wasted day" (and thus making it easier to chuck the diet), it really helped me to see that if I couldn't exercise one day, then as long as I stuck with a reasonable diet I was still getting the bulk of the benefit - it wasn't a wasted day. This may seem obvious to most of you but it was a real mental block for me.
2) Keeping meticulous track of my moods, food, activities, etc. gave me a reason to stay on my diet - I sort of view it as, I want to see what a long-term trend looks like, and if I chuck it all for a few days, then the data is compromised and I won't be able to see that.
What are your "mental tricks" to stay motivated?