I had some random thoughts tonight as I was planning my Thanksgiving meal, that might be useful for you with the big dinner coming up (I’m assuming that you are not cooking your own meal, which if you are, it will be a lot easier to keep your meal in check). You’re not going to be perfect though, and like I said before, you can’t cut all the good stuff out. Prepare yourself before you go into the meal and you should do just fine 
General tips: Don’t NOT eat the whole day before dinner. Eat a regular breakfast, lunch and have an afternoon snack. Thanksgiving is not an all you can eat buffet. Drink tons of water. Ideally you will fill 1/2 your plate with veggies, 1/4 with meat, and the 1/4 with a carbohydrate or starch, such as mashed potatoes or sweet potatoes. Wait a solid 20 minutes before you return for another helping. And really, the only thing you should be having a second helping of is veggies.
Veggies: Eat all of your veggies on your plate first. This does not include mashed potatoes or sweet potatoes. Try to arrange to have the bowl of leftover veggies sitting in front of you instead of another side or the turkey. That way, if you feel the urge to eat more, it’s in the most convenient location.
Turkey: Go with skinless, white meat portions. If you see any fat or skin on it, cut it off immediately and straight into the trash. Don’t leave it on your plate to tempt you.
Cranberry Sauce: Depending on how it’s made, this can be one of the best sides for you. As long as it hasn’t been over sweetened with sugar, you can have a good portion size.
Gravy: Skip it. Opt for a spoonful of cranberry sauce instead.
Mashed Potatoes: These will make you feel full, but then you will have an insulin crash and be hungry for more. Small portion.
Sweet Potatoes: Again, depending on how it’s made. If it’s got marshmallows on top, there’s a good chance it’s got quite a fair share of brown sugar in it. However, sweet potatoes are awesome for you, so I opt for a serving of these instead of a serving of mashed potatoes.
Stuffing: Try to avoid, but if you can’t, only take a very SMALL portion and eat it LAST.
Pumpkin Pie: Fat and calories. If you can’t avoid, try to at least avoid the crust and have a half slice. If you can, have some fresh fruit to satisfy the sweet craving instead. No whipped cream, no matter how low fat.
Other dessert: If there is another dessert option (one with fruit especially) it may be better for you than pumpkin pie (that does not mean HEALTHY… just BETTER). The best thing you can do, besides skipping it altogether, is to eat only the filling, and then, try to only eat the fruit portions (like if it’s apple pie, try not to eat the flavored gel like stuff in between the apples).
Breads/Rolls: If you can avoid having stuffing AND gravy, you can have a roll. But if you put EITHER of those two things on your plate, any bread product is out.