Some people improve dietary success with the concept of a "cheat day" - it helps in 2 major ways

1: it makes you more likely to stick with a diet long term 'cause you're not flat out denying yourself the foods you want and frustrating yourself 100% of the time. You have a cheat day to look forward to at the end of every week of good behavior; there's a light at the end of the tunnel

2: it helps to convince your body you're not starving and keep you out of "oh crap, we're going to die!" mode where your body is hoarding resources and working against you.

...and there are other benefits, too, like being able to engage in social eating every so often without feeling guilty or like you broke your diet, which is good for morale.