It’s not what you do once in a while; it’s your everyday routine that matters. So yes, you can enjoy pizza (especially when Roberta’s decides to open a pop-up-shop 3 blocks away. Please don’t ever leave!)
If it’s a weekly routine, order a salad too and split half your typical helping or take it home for lunch tomorrow.
The point is, some foods taste too good to live without. Don’t give up pizza, because what’s life without pizza? Just be reasonable (and maybe walk home afterwards!).