I remember eating whole large pizzas and still feeling hungry. Pizza is a lovely combination of flavors that is practically magical in it's ability to leave you wanting more. The fact that I can eat several slices and spend the whole time thinking, just one more piece, one more, ok, last piece... and so little time thinking about what I am actually tasting is simply fascinating. I don't know why my brain works that way -- but the more I want to restrict what I am eating, the more I tend to look down on my plate and wonder where the rest of it went while I wasn't paying attention.
Instead of thinking of a pizza as dinner, I think you'd be happier and healthier if you tweaked your plan. Make a big vegetable side dish that is filled with all your favorite veggies, and have a nice lean piece of chicken breast and then have one small slice of pizza. Eat the piece of pizza slowly, just trying to taste every bite of it -- enjoy it. Imagine you are writing a sonnet about it. How would you describe it. The more you enjoy the food, the more you should show yourself and it the respect of savoring it.
I also recommend thinking about what your favorite part is. For me, I love the crust and the tomato sauce. I can skip the cheese and still enjoy my favorite part. Other people may love the cheese and don't like the crust. How you approach including your favorite food is a really personal thing. It is unique to you.
Maybe you love pizza just as is is loaded with cheese and lots of pepperoni. If that is you, then reduce the amount of times you eat it over the course of the month. Do you eat pizza every day (like I used to), if so then reduce by 50% and only eat it every other day. And replace it with a better choice.
If you don't know what a better choice is, and you feel overwhelmed at having to think about that, then there are a multitude of ways you can approach this.
For now, think about defining your goal and thinking about how to sustain the changes on a daily basis over the rest of your life. You don't want to be your goal weight for only one day, so likewise, you can't aim for it thinking the things that you are doing to get there will only need to be done until you cross the finish line.