You don't have to unconditionally avoid dining out plans while on a diet.

After starting a diet
Whenever I had a dinner outing planned, I felt burdened first.

If you eat one bad meal
I felt like all the effort I had put in so far was going to go to waste.

However, if you keep avoiding appointments...
I actually thought it would be difficult to maintain for a long time.

While appropriately controlling the amount and menu of food
It would be more realistic to continue our daily lives together.