I basically still have the same opinion as you had. one day of bad BG is not hurting at all. but after that, i go right back to trying my best.
but, you wanted some tips for self control, so lets see:
1. try to arrange for healthy snacks -> veggies, or meat, that stuff is all carb free/ low carb.
2. if you eat the sweets/ carbs, count carbs exactly and bolus accordingly right away!
3. make your relatives aware that you are trying to stay healthy, so that they can help you make healthy food choices through the holidays, not pursuing you to stuff you don't wanna eat and providing low carb options.
4. go walking between the meals, so you still have some exercise and your pancreas/ blood sugar has some breaks.
thats all i can think of right now.
Happy holidays!