Another one to praise calorie counting apps - before I used one I would be tempted by food, and think even if I did eat it how much could it really hurt. Since tracking all my calories I find I am making much better choices about what to eat, and really thinking about the trade off of having that unhealthy snack now means little or no dinner to stay on target!
I've also found tracking the vitamins/minerals really useful using the app, as I have realised I wasn't getting anywhere near enough calcium and vitamin d each day, and have been able to make changes to my diet and take supplements.