From my experience, if you keep declining yourself stuff like that, you are setting up yourself to fail. Have that pizza, just remember to not go and stuff yourself to the point where you can’t walk because you’re full. Remember to eat slowly too.
you can also just make small modifications to decrease the calorie density of your meals, adding veggies is great.
Also, life hack: you can eat basically as much fruit as you want when dieting, it's so filling (due to the water and fibre) that you're almost guaranteed to be full and probably quite sick of it before you consume a ton of calories.
Everything in moderation. Have pizza, but limit yourself to 2 slices, have a big delicious salad with it (no creamy dressing). Small treats like this is what makes a diet sustainable.
Healthy habits stack, and maintaining a streak can be a great way to keep good habits going. If that's what keeps you going, keep doing it!
However, don't deprive yourself so much that when you do slip up you say "Fuck it" and go on a binge and eat a Taco Bell 12-Pack.
Give yourself permission to eat food you enjoy in moderation, and have a plan in place to prevent a full fall-off-the-wagon moment when you do eat some pizza and tacos.
For me, sugars and processed foods (grains especially) were an addiction. I see a lot of advice about allowing yourself a "cheat" day now and then but I would advise against it. It's like telling a drug addict it's ok to shoot up now and then, or it's ok for the alcoholic to have a drink on special occasions. Processed foods are harmful to us over time. So while it won't kill you when you are 20 or even 30, it will catch up with you.