It's nice to eat 'healthy' food, but the calorie count is what you should be watching. For example, check that calorie count mid-day and see how much you've eaten already. What do you have planned for dinner? What are you going to be doing for dinner? How's that going to keep you within your calorie count.
You can eat anything - ANYTHING (edible) - if you watch your portion sizes and accurately gauge the calorie count of what you are eating and see that you stay within your limits. Pizza? Fine. It will be lower calorie with some choices for toppings and less oil, but portion size and the ultimate count of the calories in the slice is going to make the difference. Not that it was 'healthy.' A cheesy, meaty, spicy, oily pizza slice that is very small may have the same amount of calories - but it would have to the only bite of pizza you eat!
Watch your calories like you watch your wallet on a 'cash' diet. You have this much cash in your wallet and no borrowing capability. Spend what you have (use the calories you can have) wisely. At the end of the day, you're happier. Long-term, the benefits are great.