Many forego breakfast on Thanksgiving because they know they will be eating a big meal later in the day. However, eating a good breakfast can keep you from overdoing the Thanksgiving meal.
Drinking water approximately half an hour before meals aids your digestive system, but also makes you begin to feel full, so you won't be eating unnecessary calories. This way, you can still eat all the food you want, but you'll naturally regulate your portions.
You can still have as much food as you want, but just wait fifteen minutes before you go up for your second plate. This way, the brain has time to receive the message that you're beginning to be full.
While this sounds easy, it isn't actually. Eating what you want not only refers to the food itself, but the quantity. Eat what you feel you want, but once you don't feel as excited for what you're eating, stop. This process of eating what you want will keep you entirely content, as you won't have to give anything up, but will stop you from overeating without even enjoying the food.