One thing that might help is to look at it differently: Specific goals that make your eating healthier. Less sugar is vague and hard to do. When I looked at my diet, I realized I drank lots of sugar. First I quit sodas, and they wound up tasting bad when I tried them again. Next, I cut sugar out of my coffee gradually. This bonus meant that coffee was easier to order as well.

The difference, for me, is that instead of prohibiting food - and thus, obsessing over what I can't have - I simply did specific goals and kept them up.

You can do the same thing with vegetables: To eat enough, you generally have to cut out other things, so the end result is a bonus. Sometimes it is hard at first, since you don't "like" certain things. This can be overcome with exposure and familiarity for many things, and expanded upon later on, even on things that failed previously.