How do you feel when you eat those foods?
I sometimes venture off track too, sometimes way more than I would want to. But then I start realizing how I feel eating those foods and it pushes me back to eat more fruits and vegetables. A good thing to do is to ask yourself why did you go to those foods in the first place. What is the main reason you did this? Comfort? Fear? Convenience...? Understanding the reasons better will certainly help you go passed them.
I also find that listening to/watching/reading material from Dr. Graham makes me remember why I eat this way and generally keeps my motivation high.
Another way I found helped my motivation is to make a list of all the reasons why I want to eat this way. It's on my computer now but the best would be to have it in sight as a good reminder of why you're doing what you're doing.
That might just do the trick