But if you say no thanks people might think you're a bore, depriving yourself, performatively!
"No thank you" is not performative. Here is how my aunt performatively refused a cake at my daughter's second birthday.
Me: "OK, I'm cutting the cake."
Aunt: "Oh none for me, thank you."
Me: "OK. Uncle?"
Aunt: "I mean, we already had so much food already."
Me: "No problem. Uncle, can I offer you some cake?"
Aunt: "There was just so much! All those sandwiches, the vegetables, we already had biscuits too, don't you think that's quite a lot? I couldn't eat any cake after all that.
Me: "Uncle, would you like some birthday cake?"
Aunt: "I just couldn't, it's so much. Did you make it? All that cream, and jam too? It's so much, we already ate..."
Obviously this is the point where I should have slammed the cake in her face. "Not for me, thank you" is fine!