No matter where you live in the world, society has certain norms about food.  In addition, your family or church culture might have traditions or customs about food.
Some things are easy.  If you are going to a function where food is to be served, whether its an official party, or just a visit to your Auntie's house where food is not to be refused! - go hungry (go to the event hungry).  In other words, don't add to the days calories, include what you eat or drink there as part of your day's total intake.

But what about the social norms that you can't prepare for?  What if someone bakes a cake and brings it in to work?  Or you just drop by a friends house and he or she brings out cookies?  Is it right to eat just to please someone else?  Is it right (smart) to eat just because 'everyone else is'?   I say no.  I think we are on a slippery slope when we start eating to give other people pleasure.  Consistently eating for reasons that are far removed from the main purpose which is to fuel our bodies and brains is dangerous.

To be absolutely 100% clear, food is to be enjoyed!  Tasted, savored, shared - I always enjoy eating but I do not eat to feel enjoyment.  Does that make sense?
Eating to feel good is a very dangerous habit to get into and eating just because someone suggests it, or you are bored, or you want to celebrate.. when you are really not hungry.. that is risky.  It can condition the brain to use food as a crutch or as a feel good medicine.. food should not be used as a security blanket.

It is okay to tell someone that you are too full to try their cake, or heck, that you have allergies, or that you are fasting for religious purposes, tell them anything you do not have to eat to please someone else. But if you know a food event is coming, it makes more sense to go there hungry or to bring a low calorie item to share rather than offend your host.

Please give this post some thought.  One of the reasons - and there are many - that a majority of people weigh more than is healthy for them (70% of US adults), is because they consume more calories than they need, and that is sometimes because they eat for the wrong reasons. (sometimes they eat too many calories by accident, but that is related to food labeling)